The more challenging the shot, the tighter you get, the more you'll move the club off of it's course. Additionally, when you attempt to attack tough it induces your arms to twist via impact hence narrowing the swing arc which lowers your swing speed.
There is varying golf guideline available. Hopefully, after you see this and also various other golf lessons you see that the legs play a vital function in the golf swing. If not, the very best players around the world would certainly not be using them.