Avoiding that kind of feeling is part of why I like to mix it up. A couple of days a week running, a couple days cycling, a couple days aerobics; Pilates and weight training thrown in there wherever.

The down side is that I don't really get stronger at anything unless I'm doing it three days a week. But the upside is that there's almost always some workout I feel like doing, and on the rare days that I really don't feel like any at all, I figure my body's telling me something and I give myself permission to have a day off.