IMO, you need to practice & build up slowly. Perhaps that’s the old biker in me, but almost 30 years of biking (none with a beard or Harley) have taught me to be slow in, fast out.
The IAM is a great wake-up call for your attitude & skills. I can also recommend an HGV course/test, but it’s a bit of an expensive option for your average rider (but if I had my way, the car/bike tests would have 5 hrs in an HGV to appreciate their problems).
And get into the habit of checking behind/over shoulder/mirrors before making your move - there are plenty of idiots going much faster than you & you might find one behind you.
I’ve had a couple of these in the last few months, with bikers behind me doing stupid things. Once, a biker overtook me and turned left across me, and had I not done a mirror check and instinctively backed off the throttle then I would have T-boned him. The other time, in a 30 limit in a village with lots of bollards, I was overtaking cars one at a time when starting to pull out I checked my mirror to see a biker flash past me in shorts & T-shirt doing a suicidal speed with no regard for me, the bollards or the cars that he forced into the gutter - madness. Took me ages to get my trousers clean again.
Ian