Over-reacting

I have been recovering from knee surgery well.  I am working out a bit, swimming, riding the stationary bike, doing PT exercises.  I plan to try The Shred tonight (any haters can keep it to themselves – JAYSON).  And yet, I am feeling VERY OUT OF SHAPE.  I really miss running.  I miss walking long distances.  I miss how active I usually am.  I hope I can do all of those things again…if not?  I will DIE.  Or just be a little sad…