Please tell me what i am doing wrong

you really arent doing anything specifically wrong. Its just hard to land on the board. Just keep trying and practicing and im sure youll get it eventually.

Actually, thats a nice start. try fooling around with different postures though, dont just jump straight off your board, try to use your glutes, lumbar, and abs.

-rep
And I take it that you weren't a noob when you first started

lol, same.

skateboarding: try using your arms to twist more. when you are twisting its harder to fall in one direction.
basically, if you fall in every dirrection at the same time, you dont fall.

Try rotating or bending side ways to gain balance. Bending or relaxing your knees help get you to grab the board. Also try extending ankles to do jumps off the board. I hope this helps.