In church recently, I learned that the only way to be truly happy is to be right with God.  We may feel happy here and there, but to have a true joy in your heart every single day, is to be free of sin.  It's possible that we can be saved and have a beer, or say a cuss word, but we're not going to be happy.  Having salvation doesn't keep you from sin, all if does is bring God into your life, but it's up to us to determine what we do with our lives. 
    A lot of people are scared of God's will and they think they'll end up stuck in Africa as a missionary.  But we shouldn't be scared of God's plan, it's something we should strive for on a daily basis and if we keep on his path, then he will change the desires in our hearts and we'll have true happiness in our hearts. 

I believe this is really true.  I never really knew this before, until I fully surrendered my life to God.  Once you're saved, you can do whatever you want with your salvation, but we are like investments to God, why would we want to waste that?