> If you want to enjoy short regular walks, perhaps it would help to go out for a very long and hard walk from time to time.

Bingo. Adaptation can do wonders for our perception of an activity. How do you adapt? By pushing the limits a little bit at a time; getting in the zone of discomfort for a short while, and stopping before pain/injury.

Lately, I've been trying to enjoy discomfort by thinking of it as an indication that my limits are now shifting in the right direction.