I know, huge question for a BPD but let me explain. I often have angry outburst about a situation, screaming,  crying, sulking, at some extreme point sometimes SH. 
The thing is I realize I overreacted way too late. Because AT THE MOMENT my emotions and the way I feel seems perfectly valid. 
And that's my point. With time I start to recognize when I overreact, not always. But even if I know the situation is not a big deal I still feel the need to explode. As if there was two persons in me, one rational and the other, emotional. But as long as the emotional didn't expressed the rational can't get the upper Hand. 

So, how can I let the rarional side of me take the control sooner if I KNOW i overreact and let the emotional go away ?