Dear healthybrain,
Going from experience, I would strongly advise you to reconsider your position. According to research, Cannabis is second only to amphetamines (speed) in substance induced rates of conversion to psychosis. I have personal experience with this, as I used pot as a crutch to get me through my initial depressive episode, but I had no idea the harm that I was doing to my mental health until it was far too late. Despite your misconceptions there is no such thing as 'safe' pot, especially not for people with serious psychiatric disorders
I think that you recognise the fact you do not take any other substances and applaud you for that. But if you recognise it as a vice, then why not choose to cut it out of your life as well. You gotta find an outlet, a healthier alternative to provide you with the stress relief that pot gives you. For me its running, spending more time with friends and reading. For you it can be something else. Do not try to equate people taking medication for a condition to people taking drugs recreationally. Cannabis for Bipolar is like putting diesel in a petrol engine.
I say this not for the sake judging you, its just mania and psychosis is something I would not wish on my worst enemy. In the end of the day your health is in your hands so choose wisely.
All the best,
-H