Darth Maul is more than ready to die in Star Wars: The Clone Wars season 7, which makes his death in Star Wars Rebels both more appropriate and tragic. The Sith Lord had a convoluted story in Star Wars canon, which is full of successes followed by setbacks. He can't seem to catch a break no matter how hard he tries to make things work in his favor, which is a fact he's becoming painfully aware of.
Since his miraculous return in The Clone Wars season 4, Maul has made the most of his second chance. After regaining his mind and being fitted into a set of new legs, he got to work on his revenge plan. He established the Shadow Collective, a band of crime syndicates and militant groups seeking to take the galaxy by storm. Soon after, he took the throne of Mandalore and killed Obi-Wan Kenobi's former lover, Dutchess Satine Kryze. Though his endeavors before The Clone Wars season 7 were eventful, to say the least, he still has yet to succeed at his ultimate goal of retribution on those who wronged him.
Maul orchestrated the Siege of Mandalore as a trap to lure in both Kenobi and Anakin Skywalker, however, he got neither of his targets. Instead, he faced Ahsoka Tano, who arrived to take him into custody on behalf of Bo-Katan Kryze. He gave her the chance to join him in overthrowing Darth Sidious, thus saving Anakin from turning to the dark side, but she refused. Ahsoka and Maul's subsequent fight rivaled Duel of the Fates, and ended with Ahsoka coming out on top. She saved him from a fatal drop, one he was more than willing to take, with Maul howling "Let me die!" as she used the Force to catch him. Looking at Maul's story as a whole, his willingness to pass on fits his character at that point. His destiny has passed him by time and time again and he finds existence exhausting.
Maul has consistently been one of the unluckiest individuals to exist in the Star Wars universe. He was cut in half by Kenobi, and as a result, lost the opportunity to run the Empire by Sidious' side. Since returning as a major threat, he has been out for blood against those two specifically with no luck. Eventually, the Shadow Collective crumbles as the clone war fizzles out, leaving Maul an angry shell of his former self with no direction. When he fights Kenobi for the last time in Star Wars Rebels, he loses but he finds peace in his final moments. He learns that Luke Skywalker is the Chosen One who will defeat Sidious, thus avenging both him and his old Jedi adversary.
On the surface, Darth Maul is by no means a sympathetic character, or at least he isn't supposed to be. He did some terrible things in his time and lived for the vengeance he so desired. At the same time, Maul could have been one of Star Wars' greatest heroes had it not been for those around him. Taking his complete life into perspective, one can't help but feel bad for him. He was dealt a bad hand, then tried to accomplish the status he was promised, only to fail. By the end of Star Wars: The Clone Wars season 7, he is aware that his life holds no purpose and he is ready for it to come to an end. "Let me die!" is his admittance of that, which also indirectly makes his Rebels end as perfect as it could be.