I find something to do for awhile that lets me escape my troubles - read a book, watch a funny movie etc. and I allow myself to feel the way I feel. Often times we pile guilt on top of what we are dealing with because we feel we have to fight feeling that way or that we are "weak" or something if we are having one of those days. That being said, I feel it for awhile but I make myself move on to positive things. Sometimes the mind/spirit get tired and need a little break.
I know from experience that reworking your mind is imperative to happiness, because a mind left to its own devices can become a dangerous place at times. We do have the power to change how we think, the key is to start shifting our thoughts consciously from what we don't want or what we are tired of etc - to what we do want and what we are grateful for. That energy multiplies (in either direction)
Others here suggested prayer and if you are spiritual that's a good tool. If you aren't a prayerful person that's ok too. You don't have to pray to find happiness, not all of us are religious. I practice meditation and I find with regular practice it does wonders because it allows me to free myself from mind chatter and worry etc and to access my higher awareness. It is a break and it often leads to new inspirations and being able to see answers to my problems more clearly.