You need to feel like you're making a difference. And if two years ago you didn't take a promotion and some guy next to you did, if three years ago you stopped looking for new opportunities, you're going to be bored because you should have kept your foot on the gas pedal.
Y si pasaron 2 años y no tuviste un ascenso y algún tipo cerca tuyo lo tuvo; si hace 3 años dejaste de buscar nuevas oportunidades te vas a aburrir porque deberías haber dejado el pie en el acelerador.