Question

"though i build up my persistence, i was lacking a self-confidence" is this sentence correct?

Answer 1

Even though my persistence remained consistent, I lacked self confidence.

Answer 2

You don't need to entirely re-phrase the sentence, but you do have two different tenses going there (which is a no-no).

"Though I build up my persistence" is present tense, and "I was lacking self confidence" is past.

try either "though i built" or "I am lacking"