Even though your relationship no longer exists, as a person, he still does. He’s still a walking, talking, human being you happened to share a moment of your life with, and chances are you’re going to run into him eventually.
You can move 400 miles away, you can change your hair, your wardrobe, get some new piercings, maybe a couple of tattoos, but still, you will run into him.
Because that’s how the universe works, because as big as this world may seem, and as many places you think can run away to, or as many changes you can make to yourself to feel like a new person, you can’t take back that part of your life. You can’t rewind and make it all not happen. You experienced life with him, you met new people with him, made new friends with him, discovered new places with him, and you both enjoyed all of these things together.
But that doesn’t mean you can’t enjoy them apart. Go to that restaurant with the Pad Thai you both shared together at least once a week, simply because you crave the taste. Go to the party your mutual friends invited you to simply because you want to see them, laugh with them, make new memories with them. Don’t let the chance of running into him keep you from doing whatever it is in life that you want to do.
Because what you’re doing is avoiding, not living.
Don’t avoid him, don’t even worry about him. Go to the restaurant, go to the party, do the things you want to do because you want to do them.
Don’t put life on hold. Choosing not to do something simply because he might be there, gives him control of your life even when he’s no longer in it. Don’t live with the fear that he’s around the corner, live with the confidence to know that he might be around the corner, and you’ll be ready to face him, to see his same-old indifferent grin and say hello rather than run away.
Because fear is only a feeling, and this is something you don’t have to be afraid of. He’s your ex, not The Boogeyman. And you’re his ex too, and chances are, you both are experiencing the same weird feelings, and that’s okay.
It’s okay if it’s weird and awkward and uncomfortable, but if you avoid every weird, awkward, and uncomfortable situation that happens to you, you’ll never know what it’s like to face something, to face someone.
To overcome something. Because it feels good to handle an uncomfortable situation you thought you never could. It feels good to run into your ex and be able to utter a civil syllable.
It feels good to see him and acknowledge that you both are in different parts of your life than you were when you were together, whether it’s good-different, or hot-mess I still have resentment towards you and don’t know wtf I’m doing with my life-different. Because whether you’re content with how it ended and with where you currently are in life, or whether you’re still angry and upset and just down-right disgusted, the first part of feeling closure is accepting that it’s over. And running into him often allows you to realize that the part of life you two shared together is finished.
And once you do that, you both can move on with each of your lives and not have to worry about potentially running into one another. Because you know you’ll see him again, and this time you’ll be okay with it. 
