i was writing a story in past tense and ran into a tense problem.

the sentence i was writing goes something like:

"I wanted to do for one last time ~~~~~~~~, before it was too late."

Is "before it was too late" correct or acceptable expression?

i've heard "before it is too late" many times but i don't think i have seen that expression in past tense. it just feels awkward to use it all of a sudden.

enlighten me plz~~~thx