Sometimes the repetitive pounding of running is hard on our bodies. .. and minds! Don't be scared off by it though. Take it gradually, walk part time, and vary your workouts. I enjoyed a beautiful day and a great cardio and leg strengthening workout by alternating 10 minute bouts of running with sets of stair climbing in the ravine on Friday. Alternately, do some hill repeats on a long hill, but power walk them if it feels better. Struggling through pain or injuries is likely counterproductive. One of the most fun parts of training to complete a triathlon is that even though I know I want to get X number of workouts completed in a week, I know that I can substitute sports, or other activities for some of them and still achieve my goal-AND, I'm not bored!!!
Having a specific goal really helps to keep motivated! Having a community of amazing people to exercise with keeps the spirit tank filled, and keeping the yoga brain active helps to keep perspective and balance during the journey.
Perhaps you have a spring goal too?