What do you do or eat to recover from your rides?

I had no problems in my youth doing a hard 50 mile ride on Sunday morning, then playing tennis all afternoon. Now, 40 years later, I am wiped out after a measly 35 miles at moderate pace.

Sometimes I hit on a good food regimen, that revives me. But today I am wiped out. Legs hurt, no energy, barely functioning.

What's your recovery secret?