How is he supposed to feel about it?
Pragmatic. Be thankful he's not being given his P45 today. As others have said, he might not be flying Harriers for much longer, but hey, all things must come to an end. He either flies something else, gets a ground tour or several or gets out.
He now has to face a decision as to what he is going to do with the rest of his life. Just like many of the rest of us have, before and again in the future.