No, I’m sorry we’re not a good fit.
No, I don’t think that this is the type of project I’m interested in.
I’m sorry I don’t have time for this right now.
If you never say those things to prospects then it’s time to start. You’re not the right person to serve every prospect. Sure you may be able to do the work, but you’re not going to enjoy it and the quality will suffer. That’s just going to damage your reputation.
Get comfortable with the word NO and keep that reputation strong.