- Get sb/ sth out of your mind: to stop your thinking about someone or something.
eg. i just can't seem to get her out of my mind
- Go over sth/ turn sth over in your mind: to keep thinking about something because your are try to understtand it or slove a problem.
eg. I kept turning the conversation over my mind.
- Set/ put sb's mind at rest: to make someone feel less, worry or anxious.
eg. call mother and tell her you 're arrive safety just to set her mind at rest.
- Keep sth in your mind: to remember in fact or price of information because it will be useful to your future.
eg. It's good idea, I 'll keep it in my mind.
- Your mind goes blank: informal if your mind goes blank, you suddenly cann't remember sth.
eg. My mind went blank as soos as i went into the exam room.
- Be in two mind about: informal to be unable to maake a decsion about something.
eg. We 're in two mind about whether to sell the house or rent.
- Take your mind off sth: to make yourself stop thinking about sth that is worrying you.
eg. I decide to clean the care to take my mind off the events of the day.
                      From:      Longman dictionary of contemporary English