Smoked Last night

Smoked last night. I'm away on a work trip and I think the warm temp/lonliness from missing my girlfriend made me grab a pack. Didn't touch it for 25 hours. Last night I went drinking and had 3. 2 I spit out after a couple puffs cause they were gross but the third I finished like old times. This morning I feel gross coughing again, tired, bags under the eyes. I crushed the rest of the pack and threw it out when I woke up. Never smoking again. I feel bad about it but I'm not gonna beat myself up. Posting here to be accountable though. So I went from .5 to 1 packs a day for 16 years, then cut down to 3 cigarettes a day for the few months before I quit on new years day. My question is how bad are my withdrawals going to be after 1 slip up? I'm committed to never smoking again but worried I just flushed all the hard work I put in down the drain. Thoughts?