Bleaching your hair once or twice is ok if you are careful and it's only left on for short bursts but waiting overnight and doing it again the next day is where you get into dangerous territory. It's known as 'the melt down'.
Your hair melts from the ends up if you bleach it too many times. It is easy to lose an inch or two because your hair takes on the consistency of jelly.
I always use this L'Oreal colour on my mums hair and it is never damaged, never breaks off and always gives the best blonde result. I also used this when I stripped the black out of my hair and at the moment it is a medium brown after only one 20 minute application. It's a bleach and a colour in one. Works like a charm.
Pair this lightener with the toner Fudge - Lighter Shade Of Pale and you have a white blonde colour that even Hollywood stars would envy. You can get it at supermarkets, Priceline and a lot of other places but trust me and check it out at Go Lo for literally half the price.