Manic depression?

Some one said something last night in sci fi chat. I think he was joking but it made me think a bit about how I react to life and stuff. I'd been in the room the night before and been a bit down about life and work and stuff, and had a bit of a moan and a grumble. Last night tho I was happy and cheerful and bouncy and well, yes I suppose a little bit manic. Not for any particular reason, in fact I can't place why I was so happy, just glad I was. Anyway this guy just commented on how different I seemed from the night before. 'Where's the depression from last night?', I just smiled and said it had gone. And then he asked if I was a manic depressive, just in a jokey way, not seriously, but it did make me think. I don't think I do suffer from manic depression, when I'm happy I'm not usually manically happy, and I don't usually get really depressed, tho I have very occasionally in the past. I can see how people might see me that way tho, I can be happy one day or hour or minute and down the next, but I think that is all part of being alive, part of being human? Does anyone else know what I mean?
Later on I was tlaking to Mart about death and grieving for lost loved ones, and he said that sometimes you have to go a little mad just to stay sane. That is so true. When my Nan died I don't think I went mad, I needed to because I wasn't there with my family on the night she died. I was staying over at my boyfriend's house. I'd been to see her in hospital that evening, and she was looking better, so I went to his flat instead of going home with my mum and dad. My Nan died in the early hours of the following morning, Valentines Day, and I will never forget the phone call from my Dad that woke me up. I feel guilty that I wasn't there with my mum when she went to the hospital, I feel like I should have gone home that night, not to Pete's. There is nothing I can do about it now, I can't change the past, and I am grateful that Pete was there for me to hold me and comfort me when I was distraught.

Things to be grateful for...
1. Family
2. Pete, I love him more than words can express :-)
3. Madness that keeps you sane.