This is part of what I mean by learning when it is and is not appropriate; I tried to make it clear it was not a blanket permission slip to be sloppy (anticipating that obvious misunderstanding of my point). If you end up having to seriously maintain "unclean" code, you did it wrong. You
will do it wrong before you get the hang of it, no sarcasm. Untrained gut intuitions are not very reliable here, and the only training available is practice.
And on the other hand, "maintain" is a very ambiguous word. If you are frustrated because it took you ten minutes to add one field to a form, once in the course of 3 years (to put some concrete numbers on for example's sake), you still came out ahead not spending an additional 10 hours polishing the code to a fine sheen, so you could be happy adding that one field 3 years later and saving that ten minutes. If you're frustrated because you actually have to overhaul it significantly, and it's a mess, and now you've also dropped all your context and can't remember what is what at all, and you could have cleaned up up three years ago in three hours and now lose two weeks just to understanding what the hell, then you've lost, yes. And of course "maintain" can mean a lot more than either of those two cases, too.
And as a final note, it's all gambling, and that is also something you must come to grips with. You don't really know where the changes are going to be in three years. However, you can learn to guess with a success rate much higher than mere random chance. (Don't forget to discount future time appropriately.)