my go at answering.
FCSOveride has a great answer for you right there.
I always like to relate answers to real world examples. Therefore: talk to your son next time you go around a roundabout. Ok, it's lateral 'g', but the principle is the same (get him to lean 90 degrees to the right if it helps).
Before you his the roundabout, there is no lateral 'g', right? Start going round it and he will be thrown to the outside of the car. Keep going round, and the 'g' force will remain. A loop or a break is similar.
In the case of a loop though, we already at 1 (not zero) 'g'. If I pull up into a loop with 4 'g', then that's what I will feel (initially). At the top of the loop I will be doing the same thing with my aircraft but now the plus 1 'g' I would normally feel is acting the other way so I would feel about 2 'g'. (3 'g' in the vertical). You need to picture "plus 1 'g'" acting vertically downwards at all times.
In truth no-one flies constant 'g' loops - it wouldn't look like a loop. A barrel roll is different.
For breaks, if you have the power, 4 'g' will remain the same forever. Depending on aircraft type and power available, it may reduce as, has already been pointed out, increased lift increases drag, reducing speed (unless you have more power).