한번 보자고.

A: I’m turning over a new leaf; no more bad habits.
B: I’ve heard this tune before. Seeing is believing.
A: I understand your skepticism, but I’m in it to win it
B: 한번 보자고. I wish you luck.

A: 난 새롭게 시작할거야; 나쁜 습관은 버려야지.
B: 전에도 들어본 소린데. 백문이 불여일견.
A: 네가 회의론은 이해하지만, 난 해낼거라구.
B: The proof is in the pudding. 행운을 빈다.

[Additional expressions]
*I’m turning over a new leaf
– I’m changing my ways / I’m beginning a new way of living
*no more bad habits
– I’m quitting all my bad habits / I will no longer be doing bad things
*I’ve heard this tune before.
– This is not the first time you’ve said this. / You’ve told me this before.
*Seeing is believing.
– I’ll have to see it to believe it. / I won’t believe it until I can see it.
*I understand your skepticism
– I know why you are skeptical / I get why you might not believe me
*I’m in it to win it.
– I’m dedicated to my goal. / I will not fail. / I will stick to my commitment.
*The proof is in the pudding.
– Let’s wait to see how it turns out. / We’ll see. / We’ll find out over time.
*I wish you luck.
– Good luck to you. / I wish you the best. / I hope you make it.