Not being a carpenter by trade, I make my share (and someone else's) of mistakes when building anything, I can live with them, or fix them. I'm a perfectionist, ... remember the 16" firewood) so I usually fix them. I also wind up making way too many trips to Lowes for tools I own but can't find, or material I forgot or didn't know i needed ( aka CRS ). Add to that various interruptions, such as sleeping, eating, procrastinating, keeping the woodbox stocked, fixing ATV's & mowers, tending to DW's needs, and a lot of non-building time is consumed, Were I to hatch out chicks before having proper housing for them beforehand, they'd be grown & hiding eggs all over 3 acres.
So now who's doing things backward? Huh?