Everything is relative. I know I'm still doing the HSC but I right now I would want to tell myself, "Go revise a few weeks earlier instead of a few days." But would that change anything? Not really - since I would have the same conscious and values/ethics that would possess higher leverage over what someone else (including myself) said.
Study slow and steady... I crammed a lot - which wasn't helpful. And not stress too much because I found an alternate way to get into what I wanted to study. I was devastated when I didn't get in first time round
Should have focused a bit more on finding volume of cylinders and stuff via integration and done a lot more past trial paper esp. Sami El Horsi and I would've smashed 2u.