Student or Learner
I felt good to have enjoyed those good old rainy days to the best I could though I never knew then that those moments were gonna be cherished for ever.
Perhaps something like this:
I enjoyed those good old rainy days, but didn't know then how much I would cherish the memories of those times later.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.