Stick to (one's) guns spoken language verb phrase
To indicate refusing to change one's actions or belief about something in spite of criticism.
Though her family disapproves of her marrying that poor guy, she still sticks to her gun.
Having got a lot of criticism about her fashion style, she still sticks to her gun.
Though I have to be against the world, I will stick to my gun.
Gosh, I should have stuck to my gun and refused to help him.
To be trustworthy, secure or firm.
With absolute certainty; decisively
It's mostly used in the present tense.