paulmmc

I find all the time when trying to really waste my arms i can't make them hurt, you know what i mean, like when the last couple of bench presses are really hard and painful. When doing curls or whatever i cant force the last reps, i simply can lift them until i cant anymore without an intermediate stage.
Any suggestions or good exercises?
The thing is i dont like to leave the gym feeling like i didnt push myself.
cheers guys