Hi Jujub, I have the same problem a you regarding being positive when things are going my way. I hope people won't think I'm a wimp, but when I'm stressed, something upset me or don't go my way I cry like a baby (and I can see this pattern in one of my kids. Well recently I ended up in this situation, and instead of crying I took a deep breath and repeat this 5 times, I was still stressed but not to the point of crying so I took it as a positive.
It is hard for us to see anything positive, so each day I write down 3 things I'm grateful for and one positive thing that has happened to me.