I am very content with my life right now. Things are going well and I thank God for that. But even when things aren't going the way I think they should, I know that God has a plan, and that He knows what is best for me. I know that as I come to rely more on Him, though I may not always understand the things I am going through, I will be able to endure and be content with how He sees fit to bless me.
I see people in my life though that are far from content. They aren't happy with even a single aspect of their lives. They want to change everything about themselves - from relationships to jobs to appearance - thinking that somehow that these things are the cause of their unhappiness. I see married people that seem to think if they were married to someone else everything would be better. I see single people that think if only they were married life would be complete. I have been guilty myself, thinking if I was thinner I would be happier, or if I had more money all my problems would disappear.
It seems that it is common to think that changing the outside will somehow create a sense of fulfillment on the inside. The only true way to change the inside is to turn our lives over to God. When we give ourselves over completely to Him, we change from the inside out. Our wants and desires are changed, because we want want God wants.
Delight yourself in the LORD, and he will give you the desires of your heart. Psalm 37:4 (ESV)
When we want what God wants for us, only then will He give us what our heart desires because our desires will be His. And for us to want what He wants we have to surrender to Him and give Him control of everything. It's not always easy to give up what we think we need and accept what God knows we need, but if we have any faith at all in Him, then why wouldn't we believe that He knows what is best for us.