This sounds like something based on a personal experience, so it’ll be difficult for someone else to give you an answer. But, an example would probably be; “Dear Diary, back when I was _, I made a promise with (a friend, a parent, a teacher, another student, etc.). I broke this promise because __. I ended up feeling (regretful, accomplished, safe, scared, etc.) since __.”
I think that’s the best base for something like this! Good luck!
