A merry heart doeth good like a medicine: but a broken spirit drieth the bones.
The thief cometh not, but for to steal, and to kill, and to destroy: I am come that they might have life, and that they might have it more abundantly.
Jesus Christ is life, and every good thing He created is part of that life. We get so caught up in doing and accomplishing, in working and keeping our commitments, that if we are not careful, we will come to the end of our life and suddenly wake up and realize that we never really lived. Heavenly Father wants us to enjoy life and to live it to the full, til it oveflows.
We have a choice in life. We can grumble our way through our troubles, or we can sing our way through our troubles with a merry heart. Either way, we have to go through troubles, so why not take the joy of the Lord as our strength and be filled with energy and vitality.
In John 15 Jesus talks about abiding in Him. In verse 11 He says, "These things have I spoken unto you, that my joy might remain in you, and that your joy might be full." Jesus Christ wants us to have a merry heart. He wants us to put a smile on our face so everybody around us can feel happy and secure.
Don't spend your life waiting for things to change before you can become happy. Learn to be happy now.