I know that "se" can refer to the passive voice and unidentified subjects, such as "The food was eaten" and "you take the dough and knead it for 2 minutes." I also know that you use it when a third person does something to himself/themselves.
But here's my question: What if you want to use both at the same time? There are some verbs that always get translated into a reflexive verb, like "levantarse" (to get up). What if you want to say, "If you (meaning anyone) want to succeed in life, you get up and do stuff!" Or ducharse (to take a shower): "You (meaning anyone) take a shower and you go to bed." Or "sentarse" (to sit down): You're at friend's house who has an uncomfortable couch and he tells you to sit down, and you say, "How do you (meaning anyone) sit down on such an uncomfortable couch?".
See what I mean?