I wanted to make a sentence with the words discipline and succeed.
While preparing for TOEFL I realized that if I don't have discipline, I won't succeed.
While preparing for TOEFL I realized that if I hadn't had discipline, I couldn't have succeed
For instance, I took the test 3 years ago and 10 months before the test I realized
Unless I have discipline I will fail.
In this situation I think the first sentence is correct but I am a little confused because I realized it in the past so that's why I should make this sentence for past so it's like the second one.
Thanks for answers