Before + which tense???

Dear all!

I am trying to comprehend what is happening with the word before and which is the right tense to use afterwards.

For instance: I had a conversation with a colleague before I leave for holidays. OR I had a conversation with a colleague before I left for holidays.

(** e.g. I am on holidays now does that mean I should of used left?)

Can you please clarify that for me?

Many thanks