Having a drink after quitting DOES NOT mean you failed.
A slip up may happen. It is normal. NOTHING is without hiccups.
It is natural to feel sad about it. Take your time. Remember one setback DOES NOT make you a failure.
Quit IMMEDIATELY. You STILL have control over the situation. DON'T have more drinks because of one slip.
Figure out what may have triggered this relapse and speak to someone you trust
Don't keep alone. Its best for you to get back into your support group. You need them now more than ever.
You CAN get back on track.
Sobriety is worth struggling for. Plan not to relapse.
Speak to your doctor and see what options are available, if you are struggling with cravings. There are medications that could help reduce cravings.

Having a drink after quitting DOES NOT mean you failed.

A slip up may happen. It is normal. NOTHING is without hiccups.