You might be thinking "f*ck that, a friend is only a friend if they never leave," well then yes you would be correct, but sometimes it's deeper than that, and you don't know it until you're in it.
Of course, if you go through an unfortunate loss or something monumentally tragic occurs, that friend should be at your front door. No questions asked. But sometimes, people need space for themselves. It does not have to do with you. Taking time to seek solitude and reconnect with your inner peace is not selfish. You are not a bad friend. You are human.
These "breaks" could be a day, a week, four months, maybe two years. That's something only time can tell. The key to this idea is one thing, be it very simple and yet very difficult. Kindness.
It is very, very difficult for someone in your life to not take it personally when you don't want to be around them, whether it be you no longer text one another good morning, or you just flat out have no contact for this time period. You have to be sure your exit is filled with love, loyalty, and kindness. Make it graceful, make it meaningful. You care about this person as they do you, and you need them just as much. Let them know. Let them know right now.
You are doing this to better yourself, which in turn will improve those around you.
However, if the exit is anything but kind, you could have just lost that bond for the rest of your life.
I haven't heard my dad's voice in almost four years, but I can still hear him preaching this one thought, "People will never forget how you made them feel." It gives me chills and brings me comfort all at the same damn time.
Listen, life can be unfortunate. If I'm weighing my life, the scale would definitely favor the unfortunate side significantly more than the fortunate side, but I am not bitter over it. I have acquired such an appreciation for any "good" in my life, that it actually takes up too much of my time, but I'm not changing it. If someone is making you feel good, tell them. No one is going to get annoyed to know that they are cared about.
This is certainly a scary thing that I pray you never have to decide to do, but I'm always first to drop some real-life situations on a perfectly nice day.
Being that I'm speaking of this from an intensely deep part of my current personal life, the only way I could describe what I've learned are by the quote below. These are words I will forever agonize over the fact that they spilled out of another individual's mouth before my mind could even figure out how to say it.
"That is the saddest part when you lose someone you love — that person keeps changing. And later you wonder... is this the same person I lost?" — Amy Tan, "The Kitchen God's Wife"