It is vitally important to reward yourself regularly, especially when you are working intensively. Make time each day just for you, to do things you really enjoy. Treat yourself to a good book, a spell of gaming, a scented bubble bath, or a brutal game of squash – whatever’s your thing.
All of life should be enjoyable. It is neither wise nor helpful to put off being happy until tomorrow. This serves only to make you less happy today, and an unhappy you is going to then be pining for happiness postponed rather than concentrating on what is in front of you now. Live every moment and make each day worth living.