If you want to improve your VMX riding, get yourself a trials bike and spend some time on it doing the slow stuff. The skills you learn riding over logs and boulders, up embankments and down through gullies really hone the basics of weight distribution, throttle/clutch/brake control, overall balance and body movement required with all bike riding.
Ask any of the top riders in road, motox and enduro what they do in their spare time and I bet some tight trail or trials riding will feature there somewhere.
It's great fun and something different to break the same old, same old routine of going fast. Often it's harder to go slow.