These are all very good ways to stay positive. It took me a long time to learn to do all of these myself but I really do think they work. Pop Sugar just put them all together in one post and here's my happy recap.
1. Figure out what would make you happier at work. Make sure you have a good work life balance. There's also no point in staying at a job that makes you unhappy.
2. Get things that bother you off your chest right away. Talk about them or put them in a journal. It's not good to keep them bottled up inside.
3. Don't feel guilty about leaving work on time. Your time is valuable too.
4. Buy yourself something nice every once in a while. You really do deserve it.
5. Ask for what you need at work and at home. Even if it's something small. Small things add up too. The worst anyone can say is "No."
6. Make time for things you enjoy doing. Your hobby, vacations, concerts ... everything.
Source: Pop Sugar