forgetting

I know that people have an ability to "forget" but is it true? Even so I can't use that ability freely.... I think it is none sense if I can't control... The things I have to remenber are easily forgetten, and the things I want to forget stay in my head. I think if we could use the ability to "forget" any time, our worries or suffers would dicrease or disappear and we would able to live more comfortable.