Trust the specifications. The customer (your mate, your brother, your dog) will under specify and then change the specifications. Build to spec. If spec if not clear; do not build it. Don't waste your time (you can do that a lot).

(told to me) If you want to be the smartest person in the room don't work for google. even the janitors (the people who are theoretically the bottom rung) graduated with honours at the top of their class and beat out 500 other programmers for the job, just to sweep the floor of the place.

In fact - there is always going to be some upstart 13 year old next week who taught themselves to code at age 3 and reprogrammed half the internet for fun at 15 and wants your job.