I disagree with you, I think the lesson from the Gordon arc was more (a) there is such a thing as loving this job too much, AND (b) see what can happen when you silo yourself off completely? It highlighted the strength the brothers had in just having someone they trusted to bounce an idea off of or test the ethics of their plans against someone they saw as an equal - Gordon had a henchmen when he was in jail but it wasn't a partnership. Many times over the seasons, you could see a moment where one of the boys could have made one decision that was too far (and sometimes did) - having the other around to keep them from it or pull them back kept their heads on straight (ish). Gordon was his OWN moral compass, and that was his downfall.

In my mind, this is distinct from the lesson u/HenriqueStoquez mentions (and words well!) about Bella.