How do you have a relationship Buddhism has made me realise that everything is impermanent and undergoing the process of destruction including intimate relationships however if I know this then why is it still so painful when it happens? And what is the point of trying to build a life together with another person when it's inevitably going to end? Sometimes it all feels like such a cruel joke. I was in a relationship for 15 years and never thought it would end but it did and 6 months later I still feel so sad. I don't want to ever get involved intimately with another person ever again because I don't ever want to go through that pain again. Yes this may be aversion to pain but why put yourself through that if you can avoid it? Sure there will be more pain from other things but the pain of separation from a loved one feels worse than a death. It actually feels like I could die.
Nyom Arturia,

Ajahn Chah once explained well how to have a relation, here in a simile of a glass:


  The Broken Glass
  
  You may say, "Don't break my glass!" But you can't prevent something breakable from breaking. If it doesn't break now, it'll break later on. If you don't break it, someone else will. If someone else doesn't break it, one of the chickens will! The Buddha says to accept this. He penetrated all the way to seeing that this glass is already broken. This glass that isn't broken, he has us know as already broken. Whenever you pick up the glass, put water in it, drink from it, and put it down, he tells you to see that it's already broken. Understand? The Buddha's understanding was like this. He saw the broken glass in the unbroken one. Whenever its conditions run out, it'll break. Develop this attitude. Use the glass; look after it. Then one day it slips out of your hand: "Smash!" No problem. Why no problem? Because you saw it as broken before it broke. See?
  
  But usually people say, "I've taken such good care of this glass. Don't ever let it break." Later on the dog breaks it, and you hate the dog. If your child breaks it, you hate him, too. You hate whoever breaks it — because you've dammed yourself up so that the water can't flow. You've made a dam without a spillway. The only thing the dam can do is burst, right? When you make a dam, you have to make a spillway, too. When the water rises up to a certain level, it can flow off safely to the side. When it's full to the brim, it can flow out the spillway. You need to have a spillway like this. Seeing inconstancy is the Buddha's spillway. When you see things this way, you can be at peace. That's the practice of the Dhamma.


That's the case how to possible think if having or losing a relation.

The other case is the sub-question: 


  And what is the point of trying to build a life together with another person when it's inevitably going to end? Sometimes it all feels like such a cruel joke.


Realization that becoming is actually a "curel joke" is a very high realization and if seen in all compound things the reason for earnest seeking a path out, blessed if having come to the Buddhas good teachings. This is meeting up with the reality of Dukkha.

So in regard of search, what will be for a long time benefit?
That search it self is bound to much suffering as well, is clear, but if not having a search is needed and there are three kinds:


  Iti 54
  
  This was said by the Blessed One, said by the Arahant, so I have heard: "There are these three searches. Which three? The search for sensuality, the search for becoming, the search for a holy life. These are the three searches."
  
  Centered,
  
  mindful,
  
  alert,
  
  the Awakened One's
  
  disciple
  
  discerns searches,
  
  how searches come into play,
  
  where they cease,
  
  &amp; the path to their ending.
  
  With the ending of searches, a monk
  
  free of want
  
  is totally unbound.


Search for a partner is nothing but about searching after sensuallity, maybe becoming, isn't it? Of course after a career even more... so just give it a deeper thought and maybe use you luck of independency you currently have for a more holly life to be.

At the End it's maybe worthy to say, that also searching for a relation to be able to live the holly life is actually nessesary, so admirable friend(s) are always worthy to seach for and also to invest much in such a relationship, even of course it will outardly break, but once being part of the other kind, no and never alone and without support till standing firm alone.

Mudita

(Note: This is a gift of Dhamma and not meant for commerzial purpose or other worldily gains)