I'm sure it's all fun and enjoyment while you're writing the code; but what about going back 2-3 months later, or worse, hiring additional developers on the pro

I'm sure it's all fun and enjoyment while you're writing the code; but what about going back 2-3 months later, or worse, hiring additional developers on the project? How enjoyable is it to have reams of inline server script across multiple pages with no clear structure or intent?