"Should it so happen, as sometimes is the case, that from having been deceited before, either by men or by events, there is none in whom the people trust, their ruin is inevitable."
Machiavelli gives the example of Venice, which while under attack by multiple enemies "couldn't, until her ruin was complete, resolve to make friends with any of them by restoring those territories she had taken from them, on account of which the war had been declared".
It is an interesting thought that people Of Venice didn't trust the enemies to be content and leave if the territories were returned. As if they were living out the pattern that they set in motion for themselves instead of looking to see if their adversaries were even interested in following that pattern or if their goals lay elsewhere.
Human interactions seem to have a similar aspect: past experience can be treated as a defining factor of future behaviour, therefore creating continuity and making it impossible to change the pattern (headed for ruin if the relationsip is deteriorating); or it can be treated as a singularity after which everybody is given a carte blanche. Finding the balance between the two approaches and being comfortable with your choice when to use which is an important art of master for your own wellbeing and for the wellbeing of those around you.