It's hard...but I do it.
The rest of my life doesn't stop for me during cramps/TOM so I figure that part shouldn't either. I get the worlds worst cramps but if I have to work that day -- I go. If I have to exercise that day -- I do it. Sometimes it helps to exercise later in the day after I've been moving around awhile and the crampy bloat has toned down to a dull roar. Other times it helps to take a couple of Midol and wait for those to kick in...
If it's so bad I feel like ripping out my uterus then I'll take an easy walk or rest day and skip my planned rest day that week. I try not to do this but I have found it necessary a couple of times.
No real help but I can sympathize
