He just broke up with me so I went out that same night. Why did he say be careful?

I went to a cocktail masterclass and was chatting with the barman. He was still messaging me so I sent him some pictures as we ended it on friendly terms despite it being horrible still. He said to have fun but to be careful…why would he say be careful, what does he think could happen?

He just broke up with me so I went out that same night. Why did he say be careful?
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