Harry Potter is often regarded as "the chosen one," and from the time of his infancy, he has been famous for his involvement in the first downfall of the Dark Lord Voldemort. Once he started school, he continued to stay in the thick of the action, saving his friends, classmates, and the entire school on multiple occasions. Finally, in what would have been his final year at Hogwart's, Harry once again defeated Voldemort, saving the whole of the wizarding world and solidifying his place in the magical history books.
Despite his achievements, Harry was never considered any more than slightly above average when it came to his magical ability at school. He received decent enough marks, but he never displayed the genius as a student that teachers observed in a young Dumbledore or Tom Riddle. When it comes to Harry's triumph over evil, it wasn't his great wit or skill that helped him, but instead, it was destiny. The events that surrounded Harry's life were a series of self-fulfilling prophecies, happy accidents, and the faults of Voldemort, all combining together to give Harry everything he needed to be victorious.
The Prophecy
Sometime in the year after Harry was born, Professor Trelawny made a prophecy about Voldemort. In it, she announced that the Dark Lord would mark someone as his equal and that this individual would have power that he knew not. The prophecy continued to say that this person would be born at the end of July to parents who had thrice defied Voldemort.
Naturally, Voldemort took great interest in this prophecy, wishing to extinguish any threats to his rise in power. The catch is that both Harry and Neville could have been the child to whom the prophesy referred. The fact that Voldemort chose Harry first was pure luck, and what set Harry on his journey, and Voldemort towards his doom.
His Parents Being Unarmed
The night Voldemort attacked Harry and his parents, Lily and James were confident that they were safe. Their home was protected by the fidelius charm, and the secret keeper was one of their closes friends. Therefore, their guard was down, and neither of them had thought to keep their wands close. In truth, however, their wands would have been unlikely to save them, and the lack thereof ultimately kept Harry alive.
Lily chose to stand between The Dark Lord and her son with no weapon or means to protect herself. This act of bravery enacted its own kind of ancient magic that protected Harry, resulting in the backfire that endowed Harry with more power.
Snape's Love For Lily
Voldemort choosing to attack the Potters over the Longbottoms was significant because, by chance, one of Voldemort's ranks was a childhood friend of Lily Potter. Severus Snape, who had been a loyal follower of Voldemorts up to that point, was so distraught at the part he played in the death of his childhood love that he turned to good and became a double agent and Dumbledore's more trusted spy.
Voldemort only learned of Snape's betrayal moments before his final battle with Harry, because Snape played his part so well. His love for Lily kept him fighting so that he could keep Harry alive, and also, with Snape's dying words, give Harry the information he needed to defeat Voldemort.
Voldemort's Horcruxes
Voldemort's greatest fear was death. He sought out any way he could to keep himself alive, including committing despicable acts of murder to fragment his soul and conceal the pieces in objects of significance.
When Voldemort first tried to murder Harry, he was unsuccessful because of the protective charm that Lily's death cast. If his soul had been intact, Voldemort would have suffered no further damage. Instead, his mutilated soul was unable to withstand the backfiring curse, and Voldemort's soul fragmented further.
The Magical Number Seven
While in school, Tom Riddle questioned Professor Slughorn about what would happen if a wizard fragmented their soul into seven pieces, one remaining in the body, and six residing in Horcruxes. Riddle knew that the number seven is the most magically significant number. He hoped that the quantity of seven soul pieces would strengthen the fragments, making him as close to immortal as he possibly could be.
Voldemort had not yet succeeded in creating six Horcruxes when he unknowingly transferred part of his soul to Harry. So when he was in hiding, he made Nagini into a Horcrux, believing that to be the final piece he needed. This resulted in eight soul pieces, ultimately eliminating any magical protection that the seven would have brought.
The Phoenix Wands
Harry learns of the connection between his and Voldemort's wands when he first purchases his in Diagon Alley. This connection was one of the many ways that Harry and Voldemort were similar. What he did not know at the time was that the twin cores in their wands made it so that Harry's and Voldemort's wands could not defeat each other in battle.
When Voldemort discovers this, he tries to use another wand but is foiled by the fact that Harry's wand, due to the twin cores and the shared soul fragment, could regurgitate Voldemort's magic back at him. This realization set Voldemort on his quest to find the Elder Wand, which would only further assist Harry's victory.
Voldemort's Ressurection
When Voldemort was resurrected, Wormtail needed the blood of an enemy to ensure that the potion succeeded. Since Voldemort has countless enemies, anyone's blood could have worked, but Voldemort was determined to use Harry's blood so that he could transfer Lily's protection to himself. However, this would prove to be one of Voldemort's biggest mistakes.
What he did not know was that this action tripled the already strong connection between him and Harry. Taking in Lily's protection was the final piece to the prophecy. Harry and Voldemort had been made equals by their connections, and Harry could now not die as long as his mother's sacrifice lived on in Voldemort's body.
The Deathly Hallows
The Deathly Hallows are three magical items that, when combined, make their owner master of death. They were invented by the Peverell brothers and then lost to the wizarding world. Dumbledore once sought the Deathly Hallows, but when his quest resulted in the loss of those he loved, he abandoned the search.
Harry was once also tempted by the Hallows but, by chance, Hermione didn't listen to Harry and pushed him to search for the Horcruxes instead. Ironically, both Harry and Dumbledore came closer to the Hallows when they weren't looking. Destiny intervened, and by choosing not to reunite them, the Hallows managed to reunite themselves.
The Invisibility Cloak
After it was invented by the Peverells, the invisibility cloak was passed on from generation to generation, all the way until it was left to Harry.
Out of the three Hallows, the cloak would have been the most difficult to find. It, by its nature, is perfectly concealable, leading it to have been lost to those who saught it for centuries. If Harry had not inherited it, purely by chance, he never would have reunited the Hallows. This implies that it was destiny for the descendent of the last Peverell brother to become the master of death.
Disarming Malfoy
When Harry headed into the forest to die, he had possession of two of the Hallows: the resurrection stone and the invisibility cloak. What he did not understand at the time was that he also had the allegiance of the Elder Wand, since he had disarmed Malfoy only days before.
So when Harry set out to sacrifice himself, he was in fact, already the master of death. Dumbledore told him in the "afterlife" that he had been the only one worthy to reunite them. This confirmed what Harry already knew deep down: the Elder Wand was not loyal to Voldemort, and through the work of destiny, he could return and put an end to his enemy.