I've had an imaginary friend since childhood that I still talk to.
Do you really still talk to them?
They've been with me for so long I don't want to ignore them.
I know this imaginary friend has been with you for many years but you have to move on and leave your childhood in the past. People will not think of you as a mature adult if you still speak to an imaginary childhood friend.
Why do I have to be mature and grown up? I'm feeling good talking to the imaginary friend.
We all know that imaginary friends are not real. They are fine when you are a child, but as an adult, more is expected of us.  Maybe see a therapist to find another outlet for yourself.