Losing yourself, or your "self" may start early. If your parents were preoccupied with getting their own unmet needs met, or were wrapped up in codependency with an alcoholic, or otherwise addicted partner, you may have been neglected or scapegoated. In that case you didn't develop a solid sense of identity. You were likely always looking for what the adults around you wanted, attempting to make yourself acceptable. I call that "playing to the crowd." If that was your beginning, it's hard to feel secure or good about yourself.
If you were well-loved and have a solid sense of who you are, you probably aren't reading this blog. But if you were "too loved" (pampered and over-given everything) then you may live with a sense of entitlement that's just as bad. In such case you believed the world revolved around you, and when it didn't, you crashed unable to cope. You hadn't learned coping skills.
Either of these leaves you feeling insecure and confused. And you may be tempted to give up more of you to get love or recognition.
If we lose a functional ability, like I lost function of my ankle when it was crushed in a car accident, that can be regained if we haven't lost hope and the will to work at rehabilitation. If I had been too depressed or too discouraged, trying to move it and seeing nothing happen, I might have lost my ability to walk, let alone ski. Poor mental health might have caused me physical loss. That is the first level of losing you.
Skiing the Andes proved I hadn't lost my ankle.
The second, more serious level is never knowing your own gifts, talents, or worth. Perhaps you don't like yourself, or you wonder if anyone cares because you didn't get the emotional support you needed in the formative years. You may have lost your heart.
Third is the most serious loss of yourself: you don't know what you believe. Why does that matter? Because we all act out our beliefs. We just do. So you may be demonstrating them without even knowing what they are. If you're unhappy with your life, start checking out what you believe about yourself, life, people, God, and so on.
The good news is you can find yourself. You can form a solid self. God wants you to. He wants you to love and like yourself. He does.