Relapse happens way before you pick up. There are 3 stages of relapse. First is emotional relapse which in this stage you are not even thinking of drinking, your resolve can be strong but not putting self care first and managing emotions appropriately is the first warning sign. Then comes the mental replapse where your mind starts to think about drinking (I can moderate maybe, I need to prove I don't like drinking). This is the point you need to reach out and tell someone in your support network and deal with it otherwise you move straight into physical relapse and pick up. These first 2 stages can happen over a period of weeks/months. We covered this a lot in rehab and for me I learned that there is no such thing as I "I don't know where it came from, one minute I was ok and the next I was drinking". There is a pattern and warning signs and it's up to me to notice and acknowledge them and take action there and then.
Don't be too hard on yourself, dust yourself off and learn from it. As frick says, doesn't matter what anyone else thinks of you, what matters is you loving yourself first and foremost. Take care and keep strong xx