My first confession is tomorrow and there's very little guidance as to what to actually confess

What is a grave sin? Anything that is 1) grave matter, 2) full knowledge, 3) full consent.

What's grave matter? IDK. Was never explained in OCIA.

Violating the ten commandments? I probably do that all the time ...

What's full knowledge? If I don't even know what grave matter is, how can I have committed any?

At the same time, what incentive does anybody have to actually grow and learn more in their faith when more knowledge = more culpability?

What about the endless venial sins?

Short with my wife. Annoyance with my kids. Bad performance review at work. Not sharing the gospel with my neighbor. Not calling my mom when she told me she would like it. Playing video games before reading Scripture. Being distracted while praying. Being negative and not grateful. Literally endless.

I just don't understand any of it.