Mostly it will free up the energy you are using holding things in place where they don't belong. What you may have missed with your mom took place "back there" not here but you keep it here by not having ever lived it.

Yes you may/will feel sad, maybe even devastated, lost, lonely, etc. but then you will be through the worst of it, it won't hang around being mysterious like it is now. It also won't happen all at once, your heart and mind are wonderful and where they "protected" you then by shutting down, they'll make sure the reveal goes only as fast as you're able to deal with it now, that you're older and able to care for yourself more/don't need a mom's full-time attention.