Using down time effectively

One of the ways I am trying to stay ahead of things is by using my downtime effectively ie using my RIM on the commute etc. The challenge is that while you can respond to email etc it isn't condusive for real thought. It's also amazing how stressed I get due to the lack of release via exercise etc. I had planned to get to the gym today and was very very edgy when things conspired to mess that up. I need to find a way to stay firm to my committments and not let distractions eat into that time ie I need an hour and 20 min to work out and I take a call that leaves me only an hour so I scrub the whole process. Very annoying.....