You have to begin training based on where you are at today, not where you were 3 months ago or based on an older personal best time. It can be difficult to start back up when you are use to performing at an optimal level. When I started training for my October half-marathon, I wanted my tempo and track times to be the same times I had been running in March and April. My legs didn't agree with me! They knew it was too much, too soon. Over the past 8 weeks, I've built back up to my fast tempo times and my previous track times. I love this motivational quote because it reminds me, in the moment, to use what I have and do what I can. It's not always smooth going or happy sailing as you are building back up and training for a race, but recognizing where your fitness level is and drawing on your past will get you the results you want because you are doing it safely.