I need to stop saying yes!

Do you ever say yes to something and then get the fear because you don’t quite know what you’ve said yes to?
That’s what I did yesterday at the end of a school volunteers meeting, they have these to run through health and safety, confidentiality and safeguarding, that kind of stuff, but at the end they asked how often I could volunteer, to which year group and what skills I could bring?
I think I’ve signed up to do baton twirling, nine till six, Monday to Thursday! It may not go down so well with my boss.