Much pain and misunderstanding comes from the simple gap between reality and the limits of understanding reality that the rational system suffers.
One feels slighted by another for example: if one could simply step back and see clearly the true meaning of the situation, one would be diffused. But one can't see everything as it is.
We attempt to reconcile conflicts through causal reasoning and a little projection to fill in the gaps. One cannot get inside the mind of another, so one must recreate that mind with one's own mind. But one makes mistakes! One cannot truly see all there is to see in another.
If an individual could see all there is to see in another, one would see that another is merely oneself, just from another angle, at another point in space and time. One is an expression of the universe, as is another.
This is an important reason for doing philosophy. Understanding heals. One is in great psychic pain, say from guilt or anger, and inquires into why one is in pain, and just understanding this reality can be a great relief. It objectifies the subjective; it takes pressure off of one's self, and locates dysfunction within a larger whole.
But this is philosophy's great shortcoming as well: to understand is to render the concrete in the abstract, and to render the concrete into the abstract implies a vast loss of information. One can only focus on so much at a time.
We have to be satisfied with the truth that one can never quite get at everything there is. One can understand obliquely, temporarily, in a limited way, and that is it. Satisfied with this state of affairs, we can move forward in relative peace.
