either 1..your not strong enough yet..and you need to do stuff against a wall or find some other way to strengthen yourself..or 2..your strong enough..but you dont have the balance for it yet..and the only way to get better balance is to keep practicing
but a few things..spread your fingers out as much as possible..it helps more than you think having a wider base..and bend your fingers and dig them into the ground to push yourself back the opposite way your falling
"If the moon and the stars would collide in the sky, and hip-hop was about to die, would you arrive at the mic and battle all these wack rappers together, till the last days a rap we be tougher than leather"
- Elevate your mental state, whoever said knowledge is ability was a genious -