If you find yourself putting off hard workouts because you remember how unpleasant they are, try restructuring your workout instead. No matter how painful an experience is, we tend to remember only two parts of it: the worst and the end.
Photo by US Army
It's called the "peak-end rule", and it seems to hold true both for athletes in races and even for people undergoing painful medical procedures. You can put up with a lot of pain if the peak pain is manageable, and if you felt good at the end.
To put this rule to work for you, first plan the end of your workout. If you find a sprint at the end of your run to be fun and exhilarating, keep it; but if you've been finishing hard and it leaves you miserable, plan a relaxing cooldown to end on a high note.
Next, look at the worst part of your workout. Can you make that part less awful? Maybe you can make your effort more even overall. Or if you're like me and you hate the feeling of being 5 minutes into a 10-minute hard effort, see if you can restructure your workouts so the intervals are only 5 minutes long, but you do twice as many.
Changing those two parts of your workout can make the whole memory more pleasant, even if you still work your body just as hard. Once the dread is banished, you'll have an easier time showing up to your next hard workout.
Dreading That Tough Workout? [Runner's World]