Jackie, I've been a Crossfitter for about 2.5 years, and I've found that next-day exhaustion is usually related to how well I slept; not how hard the previous day's workout was or what I ate before or after. Either way, though, listen to your body. If you're dragging, take it easy. Try doing some slow movement (walking usually works best for me) and after 10 or 15 minutes if you're still dragging, call it off and rest. But if you're feeling a bit more perky after 10 or 15 minutes, keep on with the slow movement.
A lot of Crossfitters are type "A", who can push things too far. With age comes wisdom... I'm 55 and I've learned just how much I can push and when I should back off. Do what seems right!
You make your choices, and you live with them. In the end, you are those choices.
"Strength is the mental and physical fortitude to endure, resilience to bounce back, and force to create change, allowing you to thrive in any circumstance and through any adversity." TrPAssassin