Disappointment

Disappointment sucks, whether it be disappointing yourself or disappointing others. I think disappointing others hurts a lot more though. 

Definition: to fail to fulfill the expectations or wishes of.

Disappointing yourself sucks, once you've completed an assignment knowing you didn't give your 100%, it leaves a bad feeling in your stomach. While doing the task, the fact that you're giving half effort doesn't seem like that big of a deal, but when you look back on the fact you didn't do your best, it makes you feel sick and embarrassed. Disappointing other people is even worse, when people rely on you to complete something and you don't, you know that their opinion of you will automatically change; even if they say it doesn't. The feeling of letting someone down or disappointing them really makes you rethink what you just did, the fact that you had a chance to really come through for someone and you end up falling short, it causes a horrible feeling to dwell in your stomach.