I'm thinking of quitting earlier than I said I would
Why are going to quit early?
I've done it before and never got caught or in trouble.
You should honor your work commitments. Finish the work you are paid to do.
I really just want to quit a little bit earlier.
Quitting earlier does not help the work load. You shouldn't shirk your work duties because there will just be more waiting for you the next day. This could also lead to your boss finding out and getting in trouble.