It's easy when you know your stops.
Most people these days don't realize that, for example, for a fixed ISO, [1/250, f/8] is the same exposure point as [1/125, f/11], or [1/60, f/16] etc (this is what the thumb wheel on your Nikon does in P mode - it cycles through various equivalent shutter/f-stop pairs). Give one stop here, take one stop there, you end up in the same place exposure-wise - but different composition-wise.
It's such a beautifully unpredictable world, and yet so structured at the same time. Wish you best of luck in your explorations. :)