One hundred push-ups challenge -- A slight setback

I went into Week 4 on Monday full of enthusiasm and energy. My strength was great, and I felt really confident -- I was halfway through the challenge and feeling good about the second half. And Monday's push-ups went really well -- tough, but my husband and I both completed all the sets. And then, I woke up Wednesday morning with a very angry shoulder.

I don't think it has anything to do with the push-ups -- I'm not sure yet what I did to cause this shoulder pain, but what I do know is that it's holding me back. I did the scheduled push-ups on Wednesday (I thought maybe it would loosen up or something) -- it was not a good idea.

I took Friday off, and I plan to jump back in at the beginning of Week 4 when I'm pain-free (or close to it). In happier news, my husband is continuing through the program. Just like in a race, I don't want him to stop and wait for me, and I don't want you to, either! So tell me what I'm missing -- how's your challenge going?