Sorry to hear it. I haven't had that particular procedure, but I have experienced a surgery that required me to stay out of the gym and rest. My advice is to take the recovery seriously. Rushing things and accidentally tearing something isn't worth the risk, IMO. Take it slow. You'll be back on your game before you know it. No, you absolutely won't "undo" everything you've done.
My surgeon told me that he often gets people who try to use the post op period to go on a diet, often because you don't feel much like eating at first anyway, but the 6 weeks post op is not a good time to try to drop a few pounds. Your body needs nutrients to speed healing. That said, if you're normally VERY active, you can likely gear back your calories to compensate for the loss of activity. I'd aim for maintaining your weight during this time.