Break the silence. 

When you walk in the street or in the supermarket or wherever you happen to be, look the people you see full in the face, give a nod of the head or squeeze out a quick smile. It won't hurt you to do that. It might help another person who's in a similar state.

Offer to help an old feeble person across the street, go volunteer your services in some charity. Don't hang back. Get on with life.

Just a few thoughts that may help.

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That was me. By the time I'm finished writing in this forum I always forget to check the stupid box.
So the only thing that works is to check the box before I start writing. But I can't remember to do that either.

Seven days have come and gone without speaking to anyone or anyone speaking to me, despite seeing lots of people, riding in crowded trains and buses, going to laundromat, ATM, and grocery. My phone has been on, but no calls or texts except a robo-call in Chinese, (I don't speak a word of it.) and an email from Target, with whom I've never done business and never will.  

I could vanish from the earth and not be missed. Should I break the silence or see how long it will last?  When I leave my apartment everything seems odd, as if I've never seen it before, although it is simultaneously quite familiar.  Maybe I'm in an episode of The Twilight Zone, for those old enough to remember the show.

I agree with Nadir- there is a huge need for people to get out of their own world and help others. This can be done through prayer as well as physical volunteer work.
Here are a few ideas:
Visit and pray at a home for the elderly
Visit cancer patients at a hospital
Make meals for the homeless
Pray outside and abortion clinic or volunteer at a pregnancy crisis center
Clean your chapel or volunteer in an another way. I will tell you that at my chapel- we are always short on volunteers.
Make meals for a woman who has just had a baby
Let us know how things work out for you!

I hope you don't feel as if you don't matter.  God knows you exist, and Our Lord even died for you.  Even if it seems as if everyone else has forgotten you, HE still cares.  They left Him all alone, too, during His passion. 

I agree with everyone else: make a small effort to smile at someone; make an effort to engage in pleasant conversation with the cashier at the store.  Those small things can make a difference in someone's day--and yours.  Start small, if you can. 

I used to feel as if I was invisible, too.  It's not a pleasant feeling.  But now I see that it was God's way of protecting me from becoming part of the world, and too worldly, and thus losing my soul.

Anyway, remember that you're always in God's mind.  You're His creation, and He made you out of nothing...because He loves you and wants you in Heaven someday.  So don't get discouraged!

****Do please let everyone know how you're doing.****

Interesting...
then I wonder why you posted anonymously.

Interesting...
then I wonder why you posted anonymously.

It could be that the poster feels isolated and uncomfortable with the fact that even though he lives among a lot of people he feels as though he were invisible.