"The electron tends to be in its lowest energy state." "When an electron reaches an excited state, it does not stay there but quickly de-excites by decreasing its energy (emitting a photon)." These statements are made considering an electron trapped in an infinite 1-D potential well. But these general principles should also apply to more realistic cases of a trapped electron. My question is why does the electron prefer lower energy states? This seems to be a recurring theme in all of physics and chemistry. But is it a scientific law?