No, I have to back out of a project

It's best to avoid cancelling projects. Sometimes it happens, and if so, I find it's good to be honest about the reason, even if it's mental health - people will respect it.

Hey,

Hope you're doing well.

Unfortunately, due to [reason], I will no longer be available to work on this project.

[I'd be happy to recommend the following artists who I know would do an amazing job...]

I apologise - I know this puts you in a difficult situation. Please know that I wouldn't be cancelling unless it was absolutely necessary.

Best of luck,

Potential reasons