Have a drink, you'll be more steady!
If you do paint outside the line, you can do two things to solve the trouble easy. You can wait until it's mostly cured (almost 24 hours) and cut it off the chrome with a razor, or you can get a "push stick". Mack and others make them, it's a sort of pencil like thing, with beveled rubber on the end, and it will squeegee the wet paint back into place, just like the error never happened.
Plus, you can always wipe it off and start over! No worries!
