Let friendship die natural death

Dear Carolyn: I've known my best friend, "Hal," since high school. We're in our late 30s now, and I don't have another male friend with whom I have been as close. We considered ourselves as close as brothers. But over the past five to 10 years, so much distance has developed between us that I feel like calling him my best friend says more about the void in my social life than our relationship.
When he writes me an increasingly infrequent, brief "update" e-mail, he often cites how busy he is with work and family as an excuse for not writing or calling. And in the past, he has expressed frustration with how he attracts "needy" friends who consume his time and energy. He wasn't specifically referring to me, but it made me self-conscious about contacting him.
In brief, this friendship is done. I know it. My question is about how to address that with him. Do I write him an honest letter stating that I feel like the friendship has run its course? Or do I not address it at all?
I feel like real men don't write each other emotional "breakup" letters; friendships come and go and men let it roll off their backs without so much as a twinge of regret or sadness.
Well, I have a hard time letting the friendship die a gradual death. I just need a way of acknowledging that and moving on. What would a woman do in this situation, and is that the same thing a man should do? — Needy needs advice
Carolyn says: Dude, you've got me feeling a little self-conscious now. Anyone for a spinoff, "I Miss You, Man"?
You're staring down a problem — well, more of a disappointment — that doesn't discriminate. Plenty of women also feel like complete dorks when they face the prospect of sending a "breakup" letter to a friend. They also tend to choose what you're choosing — to let the friendship die of natural causes — even knowing it's an unsatisfying end.
But what helps, often, sort of, is knowing there's no satisfying end to a relationship you'd rather keep. The sting of rejection is unavoidable, and it's a chromosome-blind sensation.
So too is this one: missing your friend. Or partner, or family member, or former version of yourself. Men miss men, men miss women, women miss men, women miss women; we cry over pets like we gave birth to them ourselves. When we don't miss our parents or sibs, it's because either they live down the street or we're too busy missing the parents/sibs we wish we had instead of the ones we got.
Maybe Real Men don't write "breakup" letters to friends (see "women feel like complete dorks," above), but they do form militaries into units that eat, sleep and train as a unit, because they know there's nothing more powerful than an emotional bond. Don't apologize for your grief.
Don't wallow prematurely, either. People at midlife do get swallowed up by immediate, proximity needs — job, family, neighbors, etc. Expect nothing, but stay in loose touch with Hal anyway; see what happens to your friendship, and your hankering for it, when those immediate needs start to ease.