You leave me numb

I often feel numb and very lost. Dont get me wrong I care, I feel and believe it or not I can even cry, but over the years I've learnt a great deal of lifes lessons, I have been high, I have been low, I have lost and very much loved, I have wanted, needed and hurt, but the most important thing is I have learnt from everyone and everything.
I feel I have been through a lot, more then the average 22 year old, but I am still here, just a little numb. I dont miss people like I did before, the words "i miss you" are said a little too often if I am honest.
When someone walks out the door time and time again, can you continue missing them as much as you did the first time they done it? Or are they taking little pieces of you each time they leave without knowing, leaving you feeling, well, nothing, numb! When someone has really walked out of your life, someone you trusted, put your world, soul and everything into, when they are gone, as soon as you shut the door, that feeling, you get, when you think your hearts going to stop, your eyes fill, your tears roll, the hairs on the back of your neck stand, legs, feel heavy, when that moment hits you, thats when you know you miss them already, before their even gone. If someone will only ever do this to you, how long do you keep going. Each time they leave, you feel the love falling out of you effortless to stop it, control it or even care.
You cant go on like this forever, you know!