I wouldn't necessarily call myself a Christian, but one Christian-faith tradition I tend to adopt every year (beyond the massive consumption of candy at Easter) is Lent. Most people give up tangible things like chocolate, or soda.
I'm giving up negativity.
Now, let me be clear... sarcasm is not negativity. (If I gave up sarcasm, it would basically be like taking a vow of silence.)
At this time of year in my office, giving up negativity is a serious challenge. The workload is heavy, the staff's nerves are raw, and everyone is sleep-deprived. "They" say though, that if you can do anything for 30 days, that it becomes habit. Even if I'm not completely perfect at positivity, anything is an improvement, right?
What will you give up for Lent? Why not try one of your own personality quirks? Perfectionism? Worry? Swearing? It's a sacrifice that will benefit everyone around you. (While giving up caffeine would just make you tired and irritable.)