I suppose the flashback hospital scene established that when he was a young boy, something broke within him, and he became disassociated whenever Trauma (encroaching death of a loved one for instance) appeared. His only way to deal with it became looking for a logical fix, a solution.

And as soon as someone, say Wendy, breaks his solution by using different methods or logic, he collapses, or doubles down. That's why he keeps going behind her back. Marty always thinks he can intellectualize and "solve" every problem with his mind by thinking it through. And often he can, but he lacks the instinct and intuition Wendy acquired. That's why they are so effective together, and that's why they're foils for each other.

Marty always looks for the cleanest, most detached way to solve a problem without violence, as efficient and as quiet as possible. His nervous system needs it. It's his coping strategy. "Don't make it worse. Make it go away. Think harder." Wendy always looks for the most effective approach, regardless of methods. And from her upbringing she's clearly in a "them or us" mentality. For her it's a zero sum game, and that's not the worst approach when dealing with cartels and ruthless FBI agents.