Question: Sorry if this question is dumb, but I don't seem to have a grasp on it.

Suppose you are on a rock in space, with no external forces acting. The rock attracts you with a force given by

$$F=G\frac{m\_1m\_2}{r^2},$$

and you also attract the rock with an equal and opposite force. The ground exerts the normal force which keeps you stationary, but what stops the rock from accelerating, however small that be?

Answer: 
One way to look at is:

1. Newton’s laws (namely action and reaction) implies that both bodies feel the same force (in opposite directions).
2. Both bodies are therefore accelerated, but in proportion to their respective masses $a = f/m $., therefore the most massive will appear not to move noticeably (compared to the other one), but it will move nonetheless, albeit in a relatively small way (determined by the ratio of the respective masses).
Gravity pulls together. Electrons on the surface of your & the rocks molecules push apart. Electromagnetic forces are gigantically bigger, but usually cancelled out by charge carriers moving to ensure things stay electrically neutral.

On a small body, gravity will be negligible, so even very little movements of your feet will see you bouncing away from each other. This is why the [OSIRIS-REx](https://en.wikipedia.org/wiki/OSIRIS-REx) and [Hayabusa](https://en.wikipedia.org/wiki/Hayabusa) asteroid sample-return missions didn't 'land' in the conventional sense.