Intensities.

My usual perspective is that, regarding 2 persons, the degree of exclusive separateness may produce discomfort, and eventually result in pain.

I do not think that being not separate causes pain, but I believe this holds a certain degree of truth for unbalanced and not entirely Love based relationships - where there is great pain inherent for both persons.

Let's take for example that you are a healthy and loving person and you wish to extend your Love to a person who is in pain.
In order to truly help that person you would have to embrace the pain, and when you are able to feel the pain as your own, you can transform it into something else (for example, joy)!

If you do not embrace the pain as your own (if you fear the state of being in pain), it will remain out of your reach, as a thing you cannot influence because you simply identify yourself as something which excludes that pain.
Or to say it in more simple terms: In such a case, whatever you do, it won't help much.

The only thing you can change is yourself.
However, what you define, experience, and identify as yourself depends entirely upon you.

I wouldn't advise you to completely separate yourself from pain, but it is surely helpful if you can 'untangle' the energies which were the cause of pain to become more clear and straightened out.

If you feel the pain to be to much, to overwhelming for you, I guess it wouldn't be such a bad idea to proceed slowly, process/embrace/allow/Love one bit of fear/pain at a time, and continue when you are ready. This is up to you decide upon specific situations.
Clear yourself, Trust Yourself, and do what you think is best at the moment!

(I'm a kinda 'kamikaze' type, I rush directly head on into things, even though moving too fast may have inadvertent consequences. :o)) However, even though in the cases where there is pain present, I feel joy too, because I'm clearing out the cause of it fast, and because of that, I become stronger, more loving and true to Myself.)

Which leads me to another important point.

As I said above, feeling pain can be a good thing too, because you can view it as a sign as to where things have gone wrong, and so you could make it well again quickly, or even improve it!

Pain doesn't have to be 'painful'.

Pain is actually nonexistent.
It is just a way to relate to certain energies. Make it a Loving relationship!
You don't have to relate to them in a painful way, if you are strong enough you can even enjoy them! (I think a very good example for this is sex.)

I think I should clarify further at this point.

Pain is not an energy state by itself. When there are certain energies/intensites present which you have not accepted, transmuted and incorporated, the ease of Flow/Connection becomes dis-ease, which in its extreme produces the experience of pain to signal you "Hey! Something is terribly wrong here, do something about it!".

Working contra this pain, working contra these intensities can delay the desired change, and the result is prolonged suffering.
Work through the intensities which are responsible for producing pain, and not pain itself (do not become insensitive to pain).

In other words:

Don't shoot the messenger. Heal the cause. Accept. Transmute. Incorporate.

Love!