> So, the solution is if you want a relationship to last a long time, somehow you have to keep the scar tissue from building up.
The key here is "if you want the relationship to last." In many relationships, people lose the desire for the relationship to last. For instance, in his contractor anecdote, he cares more about the outcome of the construction project that he cares about prolonging his relationship with the contractor. Or in the case of a business relationship, business partners want the business to be run in their own way more than the want their relationship to stay strong. Everything comes down to a desire to keep the relationship going.
There is also another aspect to the "desire to keep the relationship going". It is culture. It's unfortunate that he used a business relationship to drive home his point, because western business culture greatly emphasizes short-termism, binary outcomes and litigous behavior all of which are not conducive to long-term relationships.
With personal relationships, the same is true: consistency of behavior, personal autonomy and personal goals are all emphasized over collective concerns. These values all make it difficult to value or sustain a 'long-term' relationship that doesn't involve any direct personal benefit.
One of the reasons relationships wear out is that you can't have so many well-maintained relationships because there is not enough time to maintain them all. Some have to fall by the wayside, or you have to find a way to maintain them with much less frequent contact than when the relationships were fresh.
At the end of the day your longest-lasting relationships will be with the people nearest to you. Parents, siblings, spouses, children, close friends. All the others are at risk merely because you can't give them enough time (and they can't give you enough time). You can make some number of non-core relationships last, but you really have to choose to, and the choice has to be mutual.
Once you can safely establish that, it's not really hard work. Just need to be able to feel comfortable enough with the person to say your real honest thoughts and feelings.
I understand that for some people that is really hard to express what they are thinking and feeling, to anyone, even themselves, but if you work on that, then the rest becomes easier.
It was hard for me, this last part, and I had to find some good books and resources to help me understand myself first. The books that helped the most were Nicomachean Ethics by Aristotle, and Before You Know It: The Unconscious Reasons We Do What We Do by John A. Bargh.
Aristotle allows you to see that there is a way to find the middle in any kind of context, and that there is no really "best" in anything, or "the right way" in anything, and it really depends on the person. This allowed me to see better in others' perspectives and empathise better, and not feel too bad when there are conflicting opinions, since none of us are the same.
"Before you know it" allowed me to see how we think, subconsciously and consciously, and how some things are in our control and some aren't.
I hope this helps.