Problematic advice: So this wasn't really a game development advice per se, but my mom always used to tell me "do it right the first time around and you'll save time and effort" or something like that. This was actually more of a general advice to life itself, and at the time it probably applied primarily to cleaning my room or something, but I basically accepted it and lived by that advice for many many years, including when I started programming. As most of you will recognize, this can be an absolute disaster for productivity. Micro optimizations everywhere! Lets hand optimize that 100-iterations-per-frame-loop in assembly! Let's make sure this engine works equally well for a tetris clone as the next high-end MMO. Since then, I've shifted to a more "let's go with the simplest possible solution that will do the job for now" for almost everything, and then iterate and improve/optimize when needed. My productivity is orders of magnitude higher. You don't need "perfect", you need "good enough".

Good advice: Don't be afraid to throw out and rewrite problematic portions of code. Don't stick with stuff that doesn't do the job just because you spent significant time on it.

6 hours ago, mr_tawan said:

Good Advise "Don't do everything all by yourself"

I think this resonates with me the most, I've been in a 10 year struggle building my own engine for a game that most of the mechanics have long been forgotten, picking up an engine would have allowed me to accelerate building the game, my desire to make all the assets myself stopped me from implementing, and dont get me started on sound (opting to be silent over the hassle).

I recommend once you're reasonably skilled you should pick up one language per year at least through basic familiarity.  Even if you don't use it during your day job, you'll gain knowledge.  And when you face the inevitable layoffs, you'll be able to cite your passing familiarity when they ask about it at the interview.