How are you a failure? You stopped after a sip. If anything, it shows that you are committed to sobriety. Don't stop counting as if you are day one. Move along your new path and don't beat yourself up.
I would nip whatever told you to sip in the bud, however. Also, you should work on a plan. Mine is like a contingency plan for triggers and stressful situations or emergency cravings. I also have a few proactive steps like exercise, not procrastinating, etc.