You shouldn't forget. Bad things are there for us to learn from them. Intentionally tryig to forget is denial, not forgetting.

The more we try to forget something the better we remember it!

So just relax and look around. How many colours are there? Our world wouldn't be so amazing without even one of the colours. Have you noticed- black is there! Neither would people. They wouldn't be so strong and emotianally rich if they  never had bad days in their lifetime. So we do need black to get a colourful picture, we do need bad emotions to get life of various colours. Don't get afraid of them!  

总是唱歌，记得祈祷，睡觉

When I am bad I usually avoid to stay by myself and think about it. That is the worst thing.

I go out, everywhere, and try to speak with someone who loves me like my mother, my best friend... 

Focus on things you love and on yourself. Try to accomplish something that you can be proud of every day, and eventually the bad things will feel less painful and important.