>>76118497BPD is when you tend to switch from high and low emotions quickly. The person might have quick bursts of what seems like mania or depression, but it doesn't last more than a day.
Bipolar is when your hormones fluctuate between high (mania) and low (depression), each lasting a few days or longer. A good example of this is Mikeneko. She'll do something outrageous during a manic episode (e.g. hinting at being with a guy knowing it will upset her audience) for several days, which is then followed by a depressive episode (e.g. threatening suicide and ghosting). She can't stop doing this because her hormone levels get out of wack, and it happens on a predictable basis.
Your brain uses hormones, especially dopamine, to decide if an idea is good or bad: too much, and you'll think everything you do is right and you're invincible (mania); too little, and you'll think everything you do sucks and you're the worst person ever (depression). Some people get mania or depression after trauma, but for bipolars the body is just doing this on it's own regularly and the person has little to no control over it.
