If that is the way you are going to hunt, get some binoculars and a a proper binocular harness (not the strap that just goes around your neck). When you are still hunting, binoculars are like x-ray vision goggles. They allow you to focus past the brush and such that is blocking the view to what's beyond. I have spotted many deer this way that I never would have known were there and probably would have spooked.

One thing to remember is that a lot of times when you are busted by deer, you never even know it. They slip away quietly and undetected. It's likely this has happened to you a lot.

Take your time. Move slow. When you get tired, find a spot like you talked about and just sit for 30 min to an hour and triple check before you get back up. One time I took a breather against a tree in the snow and fell asleep for a few minutes. I was so tired (and sick) that I didn't notice a doe 30 yards away standing in the open. Until I stood up! Man I was pissed.