I'd say the top lesson I learned is that when you get a list of requirements from someone, most of the time they are not 100% set on them and if they agree to c

I'd say the top lesson I learned is that when you get a list of requirements from someone, most of the time they are not 100% set on them and if they agree to change something very minor, it can allow you to create significantly simpler solution and all parties will benefit from that. Junior developers often get lost while trying to design a super complex system, which satisfies all the requirements, while it doesn't really need to be that complex.