My advice, put constraints that make sense as you're developing an application, and marvel at how often you accidentally violate them while writing trivial code

My advice, put constraints that make sense as you're developing an application, and marvel at how often you accidentally violate them while writing trivial code. You'll realize pretty quickly that even when you know the whole area of what you're working on you still screw up. FKs might not add a lot of value on bet the company, mission critical, heavily tested code. But on less rigorous codebases they will save your ass.