Your life is kind of like a skyscraper. It hurts if someone tips you over. Also, the decisions you make in your foundational years can mess up everything that comes later.
However, most of the time, things find a way to work out. There are very, very few serious decisions. Even stuff we think is serious in the moment usually turns out to be pretty relaxed when we reminisce.
Focus on doing what you do to the best of your ability and do what is morally right.
With that guideline, make small decisions quickly and decisively and everything else will work out well.