If one is at all open to the idea of letter-writing, finds it at all appealing and discovers within oneself the motivation to continue, one becomes cognizant of certain new things.
One develops a sense of patience as one trains one's own hand to write neatly yet swiftly enough to carry one's thoughts to the page. That's the most difficult trick and quite a common complaint: it's faster to type than to write, and one's handwriting sucks anyway. And I'd be hard-pressed to convince today's generations of this, but it is quite rewarding to sit down and, over the course of several quiet weeks, practice handwriting.
With these come an attention to other details. One starts to critically examine the paper one is writing on. One takes a second look at the pen one is using. One gets excited for little things, like discovering a particularly cunning set of Japanese stationery.
One also looks forward to new stamps. One actually becomes curious about what stamps one's local post office has for sale, and one becomes excited about which stamps are coming soon. One may even become aware of a new level of drama: "The price of stamps is going up next Monday, but for some reason (shakes head, sighs) they aren't releasing the new rate stamps for another month and a half. No telling whose brilliant idea that was."
I picked up these Gulf Coast Lighthouses stamps today, but I'm looking forward to the release of the US Flags this month. When I was in the UK I'd hoped to pick up the McKean/Gaiman Mythical Creatures stamps, but no opportunity presented itself. I never ended up near a post office, and W.H. Smith was fresh out of any kind of postage.