The Shadow Side In The Signs: Aries, Taurus and Gemini
Every sign is capable of exhibiting self-destructive traits. Generally, they are exaggerated versions of the signs' attributes that result in the opposite of their primary goals.
In the following analyses I won't look at the "why" just the "how." Note that these are very general descriptions and are not meant to be in-depth analyses of individuals.
ARIES
Goals: to be first, to compete, to challenge
Courage and initiative are distorted into blind impulse. Aries can charge bravely into situations that no one else will tackle, but when driven by rage or complete disregard for self-preservation they can seriously hurt themselves (or destroy their relationships). If they're being really self-destructive, they'll pick a situation that's impossibly dangerous. Even better if others have failed trying to do the same (this gets Aries' competitive juices flowing). They hate to lose, but when they're being self -destructive it's almost as if they're daring themselves to fail.
TAURUS
Goals: to thrive, to accumulate, to preserve
Self-preservation and caution are distorted into stagnation. Taurus is a pro at amassing resources, but when they shut themselves off from all change, what's growing in their life can wither and die. The very thing that they fear the most (poverty) can be triggered if they're just surviving, rather than thriving. On the other hand, their love of good food and comfort can also be a point of self-destruction if they overindulge. They can damage their physical health through overeating and lack of physical activity if comfort turns into a passive lifestyle.
GEMINI
Goals: to communicate, to learn, to multitask
Their masterful command of information can become manic and untrustworthy. Their ability to integrate multiple sources of info will undermine them as their communication sounds like regurgitated nonsense and they contradict themselves. Their understanding of what's true and what's "fake news" can become distorted, until they're not even sure if what they're saying is the real deal. If they get caught up in what sounds clever rather than what's honest or honourable, others will stop trusting them and deny them the very thing they crave: communication.