They say "practise makes perfect", when what those that use that phrase really mean is "perfect practise makes perfect".
I spent a long time driving around without much of an idea what I was doing. I remember watching a video in which the main advice was simply to drive a certain number of laps within half a second of your personal best.
And that's fine, but it makes no reference whatsoever to whether you're actually doing it right. If your personal best is dead slow because you're driving the wrong line, or not hitting apexes, or you're entering corners too fast and therefore losing exit speeds, then all you're doing in putting those laps down is reinforcing bad habits.
As time went on I realised I needed to slow things down if I wanted to speed up. A large part of that is iSpeed telemetry analysis. But that's not all of the story. You need to be able to read a track.
I put in a couple of weeks solid at Laguna Seca, and along with a later week at Mosport, it reinforced the need to use markers, and to be consistent with use of markers.
In this video I re-familiarise myself with Spa, a place I'm reasonably familiar with already, but not a track I'm comfortable with. I demonstrate the method of analysing each corner, looking for markers as well as thinking just how to drive them. I try different things, I stop and think about individual corners, and I slow down when I realise I'm pushing too hard and not learning enough.