Have a break me ol' mucker. Couple of weeks proper sleep - they do all sorts of stuff to your sleep patterns. If you're getting all emotional they're probably damaging your physical health too, So... get down that pool of yours and regain your fitness.
Then, when you fancy it, do it, but moderate it. When something feels bad stop. Bet you've carried on even though you were already feeling this a while back? Don't overdo it again and you won't have to feel like this.
Learn your limit and stick to it. When you've edged past your limit, slow right down to compensate.
And, for immediate comfort, remember it's Wednesday and you'll feel none of this by Friday.*
*and that's not an excuse to get back on it!