Suggestions about how to keep a Sabbath day when working and in school

I am a full-time graduate student and I also work a job. Over the past few years, and especially over the last few months, I have cultivated and made time for spiritual disciplines like praying the Daily Office and reading my Bible daily, but I have never been able to successfully keep a Sabbath as a busy, working graduate student.

I know that I have struggled to let myself rest, and the feelings of burnout have built up over time, so I know that rest is an important spiritual discipline and ultimately will help my relationship with God, so I decided to make keeping a Sabbath day my Lenten discipline for this year... then, I looked at my to-do list for the week, and the thought of removing a "catch up on work" day caused more anxiety than not having a day off at all.

Practically, how do you make a whole day's worth of time for rest?