Yep great idea. I've used it myself when I'm tired/struggling for motivation. I tell myself I'm just going to the gym to stretch. Then after that I tell myself I'm just going to walk on the treadmill for 5min. Usually by then I've got the blood flowing and I get a whole workout done. Sometimes like you said it's only 5min but you've still made the effort, and reinforced the idea that just because you're tired doesn't mean you don't go. The mental strength you build in those times is worth it's weight in gold