This can indicate the past, or something you are unaware of. Or it can link with something that was ‘alive’ and influential in your life at some time, but is now left behind perhaps like a seashell on a beach left behind by what was living in it. It might therefore link with someone or something being left, or a phase of your life that has been passed through.
Idioms: Behind the scenes; behind the time; fall behind; put something behind me.
What is it that is behind, and what does this suggest is in the past or that you are not aware of?
What is it you are behind in, or how are you comparing yourself with others?
Are you now becoming aware of something that was previously out of sight?