I had the same problem mate
Start small don't worry about height just move your legs a few inches apart and then back before you land
Slowly increase the distance over a few bocking sessions (don't rush you'll only mess it up)
After a while you will start getting good at it then try another trick the same way
I can now do a semi passable straddle and spring grab (nothing special but getting there)
Above all don't get down hearted just keep trying remember most of the people you see doing good tricks have either been Bocking longer than you or have a background of some other sport that helps
Jason