Hey Rajaraman – thanks for these kind words.
My thinking around constraints and impact have been definitely evolved over time – and also in some ways, haven’t changed much 
Specifically…
Constraints have become something that I’ve changed my reception of, I think, slowly over time. Previously, I think I’d always been searching for the “judo solution” amidst constraints. That is, how can you get the maximum outcome by doing the least? And while that’s a useful frame for some problems, I think other times, in the face of certain constraints, it’s frustrating. For example, when you’re faced with certain constraints in your business (e.g., capital, people, time), yes, you can totally seek out the minimum thing to do that gets you the maximum effort. But also, I think if you want to create something special or meaningful, sometimes you have to accept that the constraint just means something will take more time – and that’s okay.
I think as entrepreneurs, when we’re faced with constraints, self-imposed or not, we can be hungry for the “hack” or elevator that zooms us up to the top. But when we don’t find that, it haunts or burdens us. Instead, I think realizing that amidst constraints, something will just take longer, is an important truth to accept. A perfect example of this I think is the writing we do on our blog. I could’ve looked for the judo solution for creating organic traffic (e.g., hire content writers + editors) – but I had a specific vision for what I wanted the content to be. And I knew that we had the constraint of cash. As a result, I’ve chosen over the past 6 years to write every single one of our 100s of blog posts myself (with maybe ~4 exceptions). And we’ve gotten incredible traffic because of it + built a loyal audience. But it also took 6 years. And I wrote everything. There was no “judo solution” because of the constraint, and I chose to be okay with that because of the vision I had in mind.
Regarding impact, I’ll say this is likely something that view hasn’t changed on. For me, personally, it’s what’s driven me to focus on this single problem (helping managers become better) for, as you noted, almost 10 years now! And for me, it’s simply because, contributing to solving a problem that is meaningful to myself and others is, well, what helps me feel alive That’s my wellspring of motivation. I think for other founders, theirs may be different – which is 100% great! But for me, recognizing that impact is my source of motivation has helped sustain and guide me in the work I do.