The secret of being miserable is to have the leisure to bother about whether you are happy or not. So don't bother to think about it! Spit on your hands and get busy. Your blood will start circulating; your mind will start ticking and pretty soon this whole positive upsurge of life in your body will drive worry from your mind.  

Get busy. Keep busy. It's the cheapest kind of medicine there is on this earth and one of the best.