The exercise of the letter

I’m at day 7 in my relationship homework and I’m supposed to write an “I’ve been meaning to tell you” letter. I’m trying to do the exercise, but I feel disgusted and reluctant. I’m supposed to write nice and meaningful sentences, but then I think that this relationship is not good enough.

I feel like a failure because this is the end of those exercises about my husband and I’m not able to make my relationship betterat least, not in the long term.

What would you advise?