> On your side-project it's also ok to ignore best engineering practice, reinvent the wheel because you feel like it or make decisions based on what seems most interesting even if it's not a 'good' decision.

Pro tip for enjoying your life at work: this also applies to you work projects. Once you realize this, you can have a lot more fun at work and even coerce work projects to be more like your for-fun/side projects. Of course this is detrimental to the company as a whole, but your company almost definitely does not care about you and you might as well extract as much enjoyment as possible.

If your coworkers are actually passionate about programming (i.e. not drones or PM brains running flowchart to increase quarterly profit), you can even make work more enjoyable for them.

Things like unconventional language choices, over-engineering of systems, unusual coding styles, obscure protocol/library use, and of course a ton of NIH can really spice up a mundane codebase.

Even stretching an "easy" module into a masterfully crafted program and going 4x over estimation can be fun sometimes (without any of the bad design choices suggested above).

Yes I stand by this bad advice, and it's allowed me to play with so much technology I would never otherwise touch at day job.