This is a very dangerous and delicate topic, I guess. But I tried to tell my views on it.

What are the main reasons for leaving a pen pal?

Sometimes we are too busy in life such as new stages, new schools, new jobs, new families. Sometimes it’s hard to manage everything and we tend to quit stuff instead of doing it in halves. Also, there are moments when we simply don’t feel like writing, we lack of curiosity, motivation and/or means. 

If you receive a presentation letter that does not seem to click with you, just reply and explain it to the person, kindly. Together you’ll be able to figure out if there’s a way of making it work, or not.  

Also, it’s not that uncommon to come across people who seem to be minded pen pals and then disappear with the wind. This will always happen inside snail mail world, whether you are a regular writer or not.  Every time I come across a report about a pen pal who was not replying letters or any type of contact, I tend to be really rigorous and delete them from my project. First because I want everything to be up to date, and people are able to ask for a “break” or to simple ask to leave. I find it rude to just not answer someone who spent time minding about us.

Sometimes it feels difficult to find the right words of asking someone about letters, without sound like we are bothering them. So my advice is to send a nice short simple message, kindly asking what you intent to know. For example:
                Dear  ---- ,
hello again! How are you? I wrote you a little ---- time ago, but I never heard back from you and was concerning if you changed your mind about us being pen pals. If you are busy at the time, I understand and would feel glad to wait patiently for your reply. If you do not feel like we are connecting or you don’t want to be pen pals anymore, I understand. Just leave me a quick message either way, I’d love to hear back from you.
               Sincerely, -----

Anyway, most of the times, I don’t believe it is directly related to us as pen pals.
It doesn’t matter your age or situation in life, things happen and circumstances not always allow everyone to keep the same regular rhythm; but, of course, there’s no excuse for even a short e-mail letting others know that you are not sending letters at the moment. First of all, I advice comprehension and understanding towards someone who we actually don’t know.

If you’re concerned that you’re not hearing from a pen pal since what it seems to be forever… before judging, try to reach the person by other means (e-mail for instance…) and ask her/him nicely how they’re doing, if s/he got your letter, and if thinks of replying soon.

There sometimes are cases of pen pals with complicated financial situations, and to those who really connect to someone who is surpassing a situation like this; it’s a perfectly valid and nice option to ask your pen pal to trade e-mails or such, while they’re unable to send letters. This way, you don’t have to break bridges with nice people you’d love to know better.  If you wish to keep a good relationship towards that person you need to take a minute out of your circumstance, and explain your situation to your fellow friend. It reminds your pen pal you are concerned about your friendship and you haven’t forgotten about them.

But, keep in mind: if, after a while, you decide you are going back to write letters, don’t just appear to someone. Sit calm and take your time catching up, explain why you weren’t able to write and always thank them for their patience towards you/your situation. To avoid any disappearing situations, just keep your pen pals posted, even if by email. (For example, if you know you’re probably going to be busy for months, just send an e-mail to your pen pal explaining it).

For example:
                Dear ---- ,
hello! I’m just leaving a quick note letting you know I’ll be ----- (abroad, busy, taking exams, moving,…)  I’m --- (sad, excited, happy, nervous,… about it) ---- and afraid of not being able to find  --- (time, money, means,…)--- .  I really don’t want to lose contact with you, and maybe around ---(x time)--- I’ll be able to write you back. I’ll probably e-mail you once in a while, anyways.

I’ll catch up with you as soon as I find a chance. Have yourself a great time, you’ll be reminded. 

                Take care, ----

You surely can write around 10 handwritten pages about how you feel, and what you’re going through; I’m sure your pen pal would feel it’s thoughtful. But, you’d write ten pages you might have used to reply her/him. But, as all in life, I think it’s better to be balanced about what you’re saying. You don’t want to overload a pen pal about a bad thing, especially when they’re not going to hear back from you in a while (or never).  And if you prefer, you don’t have to tell it all. Just keep it simple, honest and direct. Be kind and respectful at all times. 

Despite the love for letters, we are all real people who might get along or not; people who we don’t click with or those who reply our long letters with uninterested telegrams; just keep your hopes up and look forward to meet everyone the best you can before dropping without a good motive. But, when it comes to being sure you want to leave a pen pal, the words don’t come easy. I know… But, don’t feel bad. Sometimes it is what it is, and there’s no rule stating you’re obliged to connect to everybody you wrote to. Just let them know, and move forward on finding another pen pal. In some cases, if you feel it’d be an option you can suggest you both become post crossing pals, for instance.

                Dear ----  ,
It’s with sadness that I’m writing you today. I will no longer be able to exchange letters with you. I feel you are ---(nice, offensive, sweet, kind)--- but I don’t see us connecting in a real minded way as long term close friends, and I’m hoping you won’t take this the wrong way.
I’d love to keep contact if you’d like. I know you collect postcard, so I thought maybe we could be just “postcrossing pals”; would that interest you? Please reply me a quick note either way.
         Take care, ------

Basically, everything works out for the best with a bit of communication and the right amount of honesty. That fits also for making your letter friendships last. You must always keep in mind that pen palling is no difference of having a real friend in life, so you both must talk about your differences, learn from each other and educate each other on various interesting topics.  And it is not only about you, so even if you have a wide range of topics to write about and interests, don’t be too shabby to ask your pen pal if they agree/share that interest with you, or don’t.  One way of keeping it smooth and sweet, is alternating your snail mail experience with the emails and social media (Instagram and other communities such as [ex:]our Facebook private group), especially when it comes to delayed answers, lost letters, longs waits or busy times. It is a simple way of keeping your pen pal posted you’ve sent a letter or let them know you finally got theirs.