Tight is good, but crank it too much and you wreck the fitting or strip the threads. Seen it happen. The crush washer or seal needs to be seated, not flattened into paste. A lot of guys go straight for the biggest wrench and heave on it. Better to follow the torque spec if there is one. Snug it up, check for leaks after pressure cycles, then maybe a tiny extra turn.

Disagree, a dip can't be hidden, only fixed.

Piggy bank is a perfect way to explain it. I had to do the same thing with my dad, comparing a 401k to a big, locked savings account at his job. Simple pictures and stories work way better than throwing numbers at them. It takes patience, but once they get the basic idea, the rest starts to make sense. I found that using things they already understand, like a garden growing over time, really helps.