I don't get ashes anymore, as I don't consider myself so much "catholic" as I do "christian". But, I do fast. Whenever I feel hungry, I remember it is a small discomfort compared to the 40 days of fasting Jesus did, and the pain He endured on the cross.
I also try to remember to do something more positive, rather than giving up something. Giving up stuff turned out to be too easy, so it was really not much of a sacrifice. But, for instance, the other day, someone brushed me off, and I was really insulted. I started to get angry. Then I just talked myself into letting it go. I figured I was just over reacting, and maybe he just had a bad day. Today, that same person called me up. He did have a bad day, but could feel my hurt and apologized for being so short with me. I feel much better.