Relationships beget tolerance
Relationship here refers to any sort of rapport rather than a romantic relationship, as the word is sometimes used. So this could be a friend, colleague, sibling, family, romantic partner, business partner, etc.
The analogy to this quote is the stronger the bond you have with someone, the harder it is to break. Breaking that bond is a metaphor for no longer being able to tolerate whatever it is about that person, and/or what s/he did. That’s the tolerance of which I speak.
When you have relationship with someone, you have more tolerance for them and their ways. You may expect more from them than another generic person on a certain matter, like a clean house, and you would tolerate less, relatively speaking, from your expectations due to your relationship with them. But when it comes down to it, you would tolerate more when they mess up, slack off or just don’t hold up the bargain, compared to someone in the same role with whom you do not have a relationship. Of course, there comes a point where there isn’t more to give, but by that point, you’ve likely gone past the tolerance point for others.
You can also use this quote in the reverse role. If you have a relationship with someone, be sure to afford them a little more tolerance, in general. And develop all your relationships so if they ever end up getting tested, it will take more to break it.