I'm afraid of losing my best guy friend. How can I work around this fear?

My best male friend is doing paid co op now and I feel like I might lose him, which seems ridiculous because we still chat through instant messaging sometimes.

I’m really worried I will end up losing him and that he’ll end up caring about his “work” more and forgetting about putting effort into our friendship. I’m also scared he might end up falling for some woman he works with, even though I shouldn’t be.

What sorts of things should I realize right now before I do end up pushing him away completely because of my fears and insecurities?

Have you ever had fears like this? What did you do about them?