Once you show yourself some self-compassion, you can now evaluate your losses objectively, without judgment. Your losses can be broken down into two categories:
Muscle and Strength Loss
If your layoff was under three months, then chances are you did not lose very much muscle.
According to Sports-Specific Rehabilitation, "Strength trained athletes retain strength gains during short periods of inactivity (two weeks) and retain significant portions of strength gains (88% to 93%) during inactivity lasting up to 12 weeks."
If you've gone without training for longer then that, don't fret. Bodybuilders and strength athletes have long observed that even after a long period of inactivity outside the gym—sometimes lasting years—previous levels of strength came back relatively quickly. It's almost as if one's muscle retains a "memory" of how strong it once was. (Hence, the term for this is "muscle memory.")
Scientists were actually perplexed about this phenomenon until recently, when it was discovered that the nuclei of muscle (called myonuclei) actually stay in-tact even through atrophy.
In short, strength comes back quickly.