The party is cancelled!

Imagine you invite people to a party in your house. Your house has six doors. Unfortunately for some reason you had to cancel the party last minute. You still have to be at the door to tell people the party is cancelled. If you get too involved in long conversations with your guests at one door, you might even get carried away and forget the purpose of meeting people at the door. Subsequently people may enter your house from the other five doors as well. They may not even be your friends you invited, they may overwhelm you and may even cause lots of problems. So what you have to do is to quickly greet the person at the door, explain the situation and swiftly move to the other guests as soon as they appear at that door. If you are very mindful and work hard you may be able to keep your house free from all the guests.

This is something like what you do in vipassana meditation. The house is your mind. The six doors are your six senses. Greeting people at the door is similar to the six senses meeting their respective stimuli. Talking to your guests at each door and not letting them in is like reflecting on the impermanence, suffering, and non-self nature of this process and letting them go. The same way you keep your house free from trouble as in the above metaphor, you can keep your mind free from suffering during meditation.

Note: This metaphor about the house was originally taken from one of Ajahn Chah's books. I have slightly modified it here.