How do you know when you don't need to take the Paxil (paroxetine) pill no more?

Taper down. The maximization of antidepressant use is a long subject to address. Firstly, do not stop any medication without consulting the prescribing physician. If you feel functionally stable & have been able to sustain this over time, then a discussion with the prescriber is warranted. There are may factors to consider before stopping. Always gradually taper down if cessation is the agreed upon goal.
Under doctors advice. Paxil (paroxetine) is an effective antidepressant medication. When no longer depressed, and when utilizing another treatment method (counseling, exercise, meditation, self help reading, etc.), and having taken the Paxil (paroxetine) for at least 4 months, and no major holidays or anniversaries of significant or traumatic events are approaching and you have your doctor's permission and supervision, it is ok to taper off.