Lacking the courage to step out of my comfort zone when all signs are pointing towards a positive outcome. Seriously 锤心肝。
Here's a quote from Haruki Murakami to sum it up.
「But who can say what's best? That's why you need to grab whatever chance you have of happiness where you find it, and not worry about other people too much. My experience tells me that we get no more than two or three such chances in a life time, and if we let them go, we regret it for the rest of our lives.」