Precisely by not trying to chase them away or forget them :)

The more you try to fight these thoughts, the more they'll try to make themselves heard.

Meditation instructs the opposite: to leave them alone. Thoughts come, but you let them pass by.  It's not the moment to try to fight them.

If you realize that you are no longer present in your meditation and that you have got lost in your thoughts, bring yourself back to the present moment and resume your session. Maybe at first, you'll have to do this 20 times - while following just one minute of your session. That's okay! Next time it might only be 19 times and so on.

The important thing is to take a moment for yourself and practice regularly to learn how you can better manage these thoughts. If today you are getting too carried away by them, it's a good reason to practice. After all, that is the whole point of meditation ;)