Typically I write something 3 times. The first is a proof of concept, I don't care much about how it works as long as it works. The second time I put a lot more care into the 'how' but I usually still get a few things wrong enough that they are out of place and feel awkward to maintain or extend. The third time I have a really good handle on the problem, where the tricky parts are and how to tackle them. That third version will then live for many years, sometimes decades. Some of stuff I wrote like that in the 80's is still alive and well today (or some descendant thereof).

I try very hard not to get attached to code too much, refactor agressively and will throw it out when I feel it needs redoing. For larger codebases I tend to rip out a chunk between a pair of interfaces and tackle that section indpendently. I'll change either the code or the interfaces but never both in the same sitting.