Pitch attitude in itself isn't the big factor, other than as a speed control tool (in gliders). It's mostly about whether or not the position of the spot on the ground you're approaching changes (moves up or down in your view) at whatever pitch attitude you're holding, when that pitch attitude is being held constant. This is key for judging glide path on final in both gliders and power planes.
You know you are overshooting a spot on the ground (your glide is flatter than the angle that the spot represents), when, at a constant pitch attitude, the spot moves down toward the glareshield, and that you are undershooting if the spot moves up (glide is steeper).
So if you are gliding at max L/D in still air, say 30:1, and are at 500 ft agl, the spot you are heading for on the ground is 2.8 statute miles out ahead (15000 feet), and at the pitch attitude that is giving you the max L/D speed, held constant, the spot 2.8 miles ahead will stay in the same spot vertically, relative to the instrument panel.
If you lower the nose to best L/D + 20 knots when you are at 500 ft, say the speed increase drops the L/D to 20 (maybe not a very efficient glider). You pitched down to speed up, so the spot 2.8 miles out will move up in your view because you pitched over.
The key is what happens while you are holding the new pitch attitude constant. If your glide is now steeper because you sped up, the spot 2.8 miles away represents a shallower glide (a 30:1 glide) than your new 20:1 glide angle. What will happen is the 2.8 mile spot moved initially up to the new position when you pitched over, then instead of stabilizing at that spot, it continues to drift up because your glide path is steeper than the one represented by the spot.
The practical application of this is that when flying on final, and the spot is the runway threshold, your indicator that you are on the proper glide path is whether or not the threshold moves up or down in your view over the nose while holding a constant speed/attitude. If you hold a constant pitch attitude and the threshold moves down, you need to add spoiler to steepen the path, and if it moves up, you need to remove spoiler to make it shallower. In power planes, it's the same thing, but with throttle.