Maturing....

There will be times when I was so close to him yet we are so far apart. We only been apart for less than a year but... He grew up, being a matured adult and a much better person than I am.
What is this feeling inside of me?
am I jealous?
or am I sad because I can't read his feelings anymore?
The sayings "we realise things are precious once they are lost" have its own truth. Our friendship is slipping away and yet only after meeting him again that I realised.
I hate this! Maturing is a pain in the ass.