Well, a lot of things motivated me. I didn't like where my life/body were headed, once I started doing a lot of talks, I started seeing more and more pictures of myself and thinking "Whoa, I look really fat and old" haha.
The food you eat is 90% of fitness, easily. Weightloss and fatloss is about calorie deficit. Muscle growth is about ensuring you have enough calories, protein and nutrients to rebuild muscle you're purposefully damaging in the gym. "Abs are made in the kitchen" is totally true.
I have no doubt it helps with my work. It's much easier to stay focused when your body is properly fueled and you have a little exercise to balance out your blood sugar. If you don't feel like crap it's easier to get your work done.
I've also noticed people take me a lot more seriously and I have more pleasant interactions with people throughout the day since I've lost weight. It's unfortunate, but people do treat fit people better than overweight people, so that's been a positive effect too.
Keep an open mind. You can learn things from anyone or any thing. That technology you think "sucks" probably has some really brilliant parts to it.
The delete key is your friend. Don't be afraid to make mistakes. You can always delete them. It's better than not trying.
Work incrementally. Don't try to build things "big bang" right out of the gate.
Have tests. Preferrably integration tests and unit tests where needed. They will save you some day. They might be a pain to right and maintain at times, but they're critical to your emotional well-being later, trust me.
HAVE A LIFE. Work isn't everything. Don't let a company trick you into working 60 hour weeks. I've literally NEVER in 20 years seen someone work themselves into a promotion by burning the midnight oil every single night. It's, frankly, dumb. Go enjoy kids, or (non-computer-related) hobbies, or movies, or get some fresh air.... whatever, just get away from the computer for a bit.
Other than RxJS (obvious)... I once wrote a vector graphics processing engine for a small garment customization shop in Columbus, OH. It would look up your school/high school, get colors, mascots, names, etc, and generate dozens of designs based on procedural templates, and even render them onto images of garments with perspective and everything. It did all of this in a second or two, and all in the backend. I was written with C# and GDI+. Such a fun thing to write. Even cooler, when you ordered the design, it would take the vector image, generate an SVG file, and send it to the designer for approval, saving TONS of work recreating the design in Illustrator. AFAIK, that code is still backing the design customization stuff on areswear.com (although the website is not the one I worked on 7-8 years ago)