For an example of what confuses me, consider this Feynman diagram: http://www.britannica.com/nobel/cap/ofeynmd002a4.html. Here, a proton emits a photon, which has some momentum and therefore pushes the proton in the opposite direction. The photon, in turn, reaches the electron where it is absorbed. Again, the electron’s path is adjusted to keep the momentum of the system the same.
Protons and electrons are attracted to each other. The diagram has them moving away from one another. How do protons and electrons absorb and emit photons so that they pull each other together?