The difference between DRY and YAGNI is experience. Both are predicting the future, and you can only do that by having watched code evolve.

What's that saying? "Once is a mistake, twice is a coincidence, three times is a pattern".

Having to write something once, just write it.

Having to write something twice with small differences, think about it.

Having to write something three times? Consider refactoring.

I like to say:

- One hour of planning saves ten hours or programming...

- and one hour of research saves ten hours of planning.

You can also invert it:

- Ten hours of programming saves one hour of planning...

- and ten hours of planning saves one hour of research.

> - Ten hours of programming saves one hour of planning...

If the planning is done with 5 or more people in a meeting, there still might be some time savings...