I believe understanding works here.

"The moral of the story is that a relationship without understanding results in tragedy no matter how much the people involved love each other"

ODO:

understanding NOUN
2 Sympathetic awareness or tolerance:

 

‘he wrote with understanding and affection of the people of Dent’
‘Tolerance and understanding develops between Ruth and other members of the household.’

M-W:

understanding noun
3 a : friendly or harmonious relationship

a relationship based on mutual understanding

I believe understanding works here.

"The moral of the story is that a relationship without understanding results in tragedy no matter how much the people involved love each other"

ODO:

understanding NOUN
2 Sympathetic awareness or tolerance:

‘he wrote with understanding and affection of the people of Dent’
‘Tolerance and understanding develops between Ruth and other members of the household.’

M-W:

understanding noun
3 a : friendly or harmonious relationship

a relationship based on mutual understanding