Don't fight with these distracting thoughts. Don't strain or struggle. It's a waste. Every bit of energy that you apply to that resistance goes into the thought complex and makes it all the stronger. So don't try to force such thoughts out of your mind. It's a battle you can never win. Just observe the distraction mindfully and it will eventually go away. It's very strange, but the more bare attention you pay to such disturbances, the weaker they get.