I didn't mean to mess with your head, man, lol. But I'll take a stab at addressing your post.
Keep in mind you (and quite a few of you guys here) are WAY more analytical than I am, and that isn't a bad thing. It helps you progress, and that is what matters, so keep on keeping on how you are comfortable. But in the context of my post, just remember I'm just a dumb meathead that moves heavy $h1t because it feels good...
Is there something ... on the mental side that will let me "dig deeper" as it were?
This to me is where the rubber meets the road.
The measure of a man is what he does when no one is looking, what he does in the face of adversity, and how he deals with change. There are people that will never start because it is hard. There are people that will quit when it gets hard. And there are people that are going to push back into the face of hard, and kick hard's ass.
Hard is going to be relative to the individual. And kicking hard's ass doesn't have to mean grinding out every rep every workout, and squatting until your nose bleeds. I find change hard, switching gyms can set me back weeks. But then again, my max pull is in the low 500s and my first warm up set starts with 225, that doesn't mean someone who's max is 135 isn't kicking hard's ass too.
But, to get to the point. There comes a time, when you are doubled over, head spinning, and you think about stopping. You think you've done enough... And then, then something happens. The world slows down, life stops living you, a calm rush over comes you. A bead of sweat falls from your nose, and you hear the splash on the ground, you smell the sweet sent of victory, of pain, and of domination. In that moment you know you have more.
You can't manufacture this, and I think everyone is capable of getting there. It is just very few are willing to put in what it takes to get to that point. And then you realize you have. You gave blood and guts, time and pain to get here. You gave back, you punched the suck right in the mouth and shouldered every load you have had to bear. You realize you are the production of tens of thousands of years of evolution, and you'll be god damned if you aren't going to act like it.
Then you stand up, grab your heart, re-affirm its contents, and smash the life out of the next set, you make that bar your bitch, and smile every second of it...