The first time Goku transforms into a Super Saiyan in Dragon Ball, the hero commands Gohan to leave the general vicinity because he doesn't believe he can control the burning fury and bloodlust boiling within him...even against his own son. This moment promised a deadly new side to Goku that would require him to grapple with the negative aspects of becoming a Super Saiyan every time an opponent forced him to transform. The multitude of Super Saiyan levels that followed could have introduced both deadlier and a higher number of downsides to unlocking them. But this never really happens.
It's almost as if mangaka Akira Toriyama forgot the effect the transformation can have on a Saiyan. In fact, this is the case for every other Saiyan who has ever achieved this form. The first time every Saiyan transforms into a Super Saiyan, they always succumb to its negative impacts. The transformation is usually contingent on them experiencing intense rage, altering their personality and actions dramatically. But afterwards, every proceeding transformation is depicted as a seamless process, almost as natural as breathing.
The most egregious example of this is Goten. Similar to Dragon Ball Super's Caulifla, who first transforms by focusing her energy between her shoulder blades, Goten learns to transform instinctively, probably by employing the same method. Aside from the lame excuse of S-Cells to explain how Trunks and Goten transform so early in life, it's perplexing how children, who are naturally immature as a result of not having finished developing mentally, have a seemingly better grasp on their emotions than adults when transforming. Children are more susceptible to fits of anger that usually go unprovoked. How can these mere children be immune to such intense emotions?
Probably the best depiction of what a Super Saiyan should act like or manifest as is, ironically, a transformation that many fans wish to forget: The False Super Saiyan that Goku unlocks during his battle against the eponymous villain in the film Lord Slug. It's abundantly clear that anger drives this transformation as Goku yells throughout its duration. Although all Super Saiyans are more aggressive the first time they transform, they are still able to speak. But as a False Super Saiyan, Goku either can't or chooses not to, which is a stark contrast to how he normally fights. Further underscoring how rage fuels the False Super Saiyan form, the power immediately fades once Goku becomes startled and loses hold of his mounting fury. It's more akin to Broly's Legendary Super Saiyan transformation, which all non-Legendary forms should emulate, just to a lesser extent.
Super Saiyan 2 follows the same pattern as the first. Initiating this ascended form requires Saiyans to experience a more acute level of emotional upheaval, filling them with a profound sense of remorselessness. Gohan's personality undergoes such a terrifying transformation when he first taps into this power against Cell, causing the boy to torture the Android mercilessly rather than kill him, much to his father's horror. This dynamic is, unfortunately, never explored further. This is especially ironic in Gohan's case. By the Buu saga, he's more focused on his professional life than training, so shouldn't he be more susceptible to the form's negative effects?
Not including Dragon Ball GT's Super Saiyan 4, which can cause Saiyans to adopt a few of the same temperaments as Great Apes but to a lesser extent, all forms beyond Super Saiyan 2 either don't have an effect on the Saiyan's mental state or actually calm them down (i.e. Super Saiyan God). Mangaka Akira Toriyama set himself up with ample opportunities to explore the many potential downsides of the Super Saiyan forms, which would have both added an additional dynamic to every Dragon Ball fight and even forced these overly powerful Saiyans to rely on other means to ensure victory rather than them being trigger-happy with their transformations. But he didn't.