Piston won't retract

Scenario 1:
Stack 2 blocks powered by levers and put a piston as shown below.
P=Piston L=Lever B= Block A=Air
A B L
P B L

Break the bottom block and then the top and you'll get an infinitely powered piston.
Scenario 2:
Put blocks as shown:

A B L
P A A

And then flip the lever and put a redstone dust 1 block behind the piston and break it to create a powered piston and then you can break the block that the lever is on.