You sound like me, lol! Back in March I was hating the idea of starting to workout again because I'd drifted away from my daily 1.5-2 hr. walk/jogs. I had even checked the mileage and I was covering 8-9 miles, and sometimes, because exercise is so addicting, I'd cover 11-13 miles. Of course, I'd go past the two-hour mark on those days. But you know what, in no time, I'm back to 7 miles a day and I'll even take a day off to give the muscles and joints a break. I couldn't take a day off without major guilt in the past. I do admit, I went overboard by the third day of starting this back up and was working out 1.5 hours a day from that day on. I've got a tweak in the back of my right knee, but I think it will work itself out. Get right back on that horse. Your body will recover and your muscle memory will kick in. You're not as out of shape as you think! You might just be using different sets of muscles right now.