Why does my computer keep shutting down?

earlier today I was trying to set my computer back to normal if I was able to, because it used to give me a hour before it shut down when i had no plug in. But now it turns off after about 10 minutes. So I went to current power plan to see if I could set it right again where I had a hour without the plug in. well I guess I tough something wrong... because now my laptop shuts down for no reason and my plug is plug in. So why is that happening? I have a toshiba, I am going nuts here and not too happy!!! I don't care about the hour part anymore I just want to know why my laptop is turning off when the plug is hook in the laptop