When I was in 6th grade, our CCD teacher (which apparently stands for "Confraternity of Christian Doctrine"...Sunday school for Catholics, not necessarily on Sundays) made us go around the room and announce what we were giving up for Lent. (Of course, when I tried to do this when I was a teacher, one of the students wisely remarked, "Shouldn't it be something private between you and God? And we shouldn't brag about what we're giving up, otherwise it won't count. Kind of like birthday wishes." Smart kid.) It quickly became a contest to see who could come up with the most extreme Lenten observance ("I'm giving up breathing!" was when our teacher drew the line, as the kid next to me proceeded to turn blue while everyone else laughed). When we settled down, one of my peers said, "I'm giving up time." Pretty profound stuff for a 13 year old (and it freaked the rest of us out how well he sold this "joke" straight-faced. We all started to giggle until we realized he was serious. Then we were just confused). It turns out that his "giving up" of time was simply time spent volunteering with his family at a local food bank.
While Lent is a time commonly associated with sacrifice, consider how "giving up time" might be the most fulfilling sacrifice you could aim for. A blessed oxymoron, if there ever was one.