“Enthusiasm makes the difference.” 

-Dr Norman Vincent Peale  

Enthusiasm is what makes life better, without it your life would be bitter. If you are enthusiastic about things, you'll notice that you'll have more fun. Your life will continue to be bitter until you change your attitude. For example, let's say your parents are going out with some of your relatives and they are forcing you to go, you'll have the worst time in those couple of hours if you're complaining the whole time.  You have to enjoy it, even if you didn't want to go. You have to make the best out of it.  Being confident is one of the steps toward enthusiasm, you have to build self esteem. If youre not enthusiastic, fake it. It'll eventually come to you.