Fully known
"You have searched me, Lord, and you know me. You know when I sit and when I rise; you perceive my thoughts from afar. You discern my going out and my lying down; you are familiar with all my ways. Before a word is on my tongue you, Lord, know it completely. You hem me in behind and before, and you lay your hand upon me. Such knowledge is too wonderful for me, too lofty for me to attain."Psalm 139:1-6

"You know when I sit and when I rise." Notice how small-scale the Psalm is. It doesn't talk about the big moments of your life. It talks about the moment you sit down on the couch, tired, at night, and the moment you get up in the morning without wanting to. God is paying attention in those hours no one sees. The ordinary hours. The hours when you think you don't matter to anyone.
Maybe you've gotten used to not being noticed. To doing everything and hearing very little "thank you." To keeping what you feel to yourself because no one asks. And a tiredness built up inside, a wish to disappear, or the feeling that, if you disappeared, it would take them a while to notice. If that's where you are today, I'm so sorry. That pain is real. And it's exactly to that pain that God says: "I saw."
"Before a word is on my tongue you, Lord, know it completely." You don't need to know how to explain what you feel. You don't need to find the right words to pray. God already knows the sentence before it comes out. There are days when prayer is just a sigh, and he understands the whole sigh. "You hem me in behind and before, and you lay your hand upon me": not to trap you, but to hold you.
David ends this passage unable to understand it: "Such knowledge is too wonderful for me." He can't measure the size of this care, and you don't need to either. You only need to let it be true today. Someone sees all of you. Someone knows where you've been. And he hasn't looked away.
How to pray with it today
Today, at some ordinary moment in your day (sitting down to eat, lying down at night), stop for an instant and say: "Lord, you see me here." That's all. You don't need to ask for anything. Then tell him one thing no one knows you're feeling. He already knows; but doing this is how you stop carrying it alone.
A short prayer
Lord, you have searched me and you know me. You know when I sit and when I rise, even the words I can't manage to say. When I feel invisible, remind me that I am seen by you. Lay your hand on me today. Amen.
To keep today
In the hours no one sees, God is watching. You are fully known, and loved anyway.