How do you get to the point where you get a feeling of satisfaction just from writing good code?

Iterative development helps me. I'm working on a considerably big project for one person, even if it's tightly scoped. If I was basing my enjoyment on seeing it complete, I'd never get anywhere. Instead, I iterate on as small of a working codebase as possible so that I can successfully compile and run and see my changes impact the product.

Even in your example of writing a rendering framework being tedious: there's no reason for the renderer to be feature-complete before it can compile. My first step was just getting a window to show up with a black screen. Then I got a triangle to show up. Then I grabbed a pre-built model and got that to 1) show up, and then 2) show up without depth bugs. Each step came with the high of having solved a problem with code.

Granted, I had a little extra work on the first cycle getting some of the "slottable" framework elements in place, like when I wrote the code that renders with an arbitrary shader. That was a longer push, but the "hard parts" are all about discipline anyway. Now, with that part of the framework written, I can sit down and program/tweak a single shader and test it in my game rather quickly.

Someone mentioned above as well, that part of this will come with time: as you get more experience, what takes you a week currently might only take you a day or a handful of hours in the future. Experience will also let you set more appropriate milestones and goals. I generally try to aim for only what can be done by the end of the day, and it keeps me focused, productive, and amused, because I get to fully solve the bite-sized problems I've selected more often than if I was just pursuing a month-long task.

TL:DR: set shorter goals and you'll be able to enjoy the fun of solving them more often, keeping your morale up.

I can actually see my progress as I complete each sub-problem and (over time) see the solved sub-problems coming together to eventually form the whole program.

I use a version control system (git) to track everything I do, and I can say that reviewing the commit log (from time to time) can be very encouraging.

I would typically look at my history for the past week, and see that I've made considerable progress, which would keep me motivated to make further progress. There are weeks where I'm not nearly as productive, but whenever that's the case, I just look further back.

Well you guys provided very helpful advice and I thank you very for that, but please let me rephrase my question.

How do you get to the point where you get a feeling of satisfaction just from writing good code? I don't want to have the finished product of my code my only way to satisfaction and happiness.

Thank you all!

Also, I may get yelled at for this, but is programming really what you want to be doing? You don't want to be twenty years down the road, in a job you hate.