You accidentally said "Yes" but meant "No". Here's how to walk it back gracefully within 24 hours:
The Honest Redirect: "Hey, I said yes yesterday, but after sleeping on it, I realize I don't actually have the bandwidth to do this justice. I need to step back."
The Schedule Conflict Discovery: "I just double-checked my calendar and realized I have a conflict I completely forgot about. I won't be able to make it after all."
The Energy Check-In: "I was running on adrenaline when I said yes. Now that I've had a moment to think clearly, I need to decline so I can honor my other commitments."
Remember: It is far better to walk back a premature "Yes" within 24 hours than to commit and flake later. People respect honesty more than forced participation.