I write letters every so often, and you're probably going to get a birthday card from me in the mail if we've met more than 3.2 times. Why is this? It isn't because I'm kinder than you are - it's because I love mail. And typically speaking, the more you give the more you get. And really, receiving any kind of handwritten mail is just so romantic to me. Even if it's from someone whom I have no romantic feelings for. It's just a sweet thought to think of someone sitting at a desk for a minute and writing out my address with their fingers. Fuck, that's so nice.

Why is it great to write letters or send cards?

No one has any time to be calling all the important people in his/her life every week or even month - but a letter is so much easier to write and send, in my opinion. And the best part? It's one way. They can choose to reply or not! I love that!
Whenever people go away, they will usually always send me a postcard since they know how into correspondence I am - and I love postcards. Pictures of great places, with words about how great it is? Yes, please!
The amount of effort put into writing and sending any form of letter or card is so minimal, but that same effort seems so large when received. And that's great! Minimal effort, but with a nice payoff.
One day I will be dead. And how will you know it? You'll stop receiving cards from me. I really think a lot of people will find out that way, about my death. Is that abnormal to think about? I think I like it. Someone off somewhere just going, "Hmmm... Liz hasn't sent anything this year. She must have passed on. Sad." That idea seems so nice to me. (I'm taking liberties with assuming the "Sad." line, I realize.)
Sometimes people forget that you love or care about them. And really, there are so many people in all of our lives, it's hard to keep track of them all especially when we're so invested in our own junk going on. So sending something once in awhile is just a gentle reminder that, "Hey! You're being thought of!" Which, I think, is always an instant boost.

Now if you're sitting there going, "Hey dummy, y'ever heard of email?" -- don't speak to me like that. Email is wonderful. My problem with it is that it's too fast. Sometimes I don't want to write to someone and know that I'll get their reply instantly. I feel like doing that lessens whatever words we've exchanged. Not because they weren't meaningful, but because the whole experience was too quick for me to put any value in it - and likely, I'll forget about it even more quickly and move on to other things going on in my day. Everyone's in such a hurry, and I don't want to be in a hurry with them.

Even if you do it once a year, please mail someone something. Guaranteed it'll make them happier for even just a second.

I didn't intend for this to be so long, I apologize. If I had your address, I could've just mailed this to you and saved us all some time.