Evo, if you're up on a ladder cutting it, be sure to try to keep an arm around the part of the tree you aren't cutting. That way if it does manage to knock the ladder out from under you, you're hanging onto something that isn't going to fall (how you get down after that, I don't know, but your odds are better dropping down from a tree branch you're dangling from than falling backward with a ladder and branch landing on you). Even better, before starting to cut, tie your ladder to the tree trunk to stabilize it. But just climbing a ladder resting against a tree is hazardous enough. You're not exactly leaning against a stable, flat surface, like the side of a house.