I used to be late ALL the time too. Was known by everyone in my life as running on "island time" lol. When I was trying to change this behavior, what I did in the beginning was lie to myself. If I had to be at a place at 10 am, for example, I would tell myself I had to be there at 9 am. I struggled a little but eventually it worked. Now I don't lie to myself, if I have to be at a place at a certain time, I always make it the case that I get there at least 10 minutes before the time I'm supposed to be there. Sometimes I am late but then it is legitimate lateness due to traffic, train problems, etc.
For most of my life though I've always been late and I remember feeling so helpless and hopeless that the behavior would never change. It made it feel like it would be impossible to ever function as a normal person, and that life just wasn't for me. It wasn't the only reason to want to ctb at the time, but it definitely compounded the problem. I also think in my case, being late all the time was tied to anxiety and depression. I had anxiety to leave the house, see people, feel the need to look perfect, etc. At the time I didn't realize it though. Maybe your lateness is tied to something deeper?
