My friend becomes upset when I give constructive criticism on one of his essays. Help?

You've got the words already. Be honest. "It seems like you only want to hear from me that your essays are 'wonderfully written' ". When you try to give helpful feedback, he doesn't take it well. If he doesn't want more than an ego boost from someone that cares about him and really wants to help--- than he should find someone else to read his stories and look at his drawings. When he's ready to accept your opinions, than you will give it to him. If he has trouble taking criticism from people that support him--- imagine how he would do as a professional writer. Give him some time and he may come around and see the light.