On the advice of my doctor, I have moved from a beta-blocker (slows heart rate) to an ace-inhibitor (vasiodilatator) for purposes of a better workout this summer. Last year I lost 25 pounds (and subsequently gained it all back over a particularly stressful winter) so am looking forward to an even more successful summer this year.
Additionally, I am no longer limiting myself to The Path. The kids have found a new multi-purpose park in which to engage, which is connected to a miles-long, riverside path. Timing-wise its perfect for an hour-long 4-mile workout.
Daily perseverance is key. Anything I do - no matter how insignificant - is better than doing nothing.