I have made enough mistakes and done enough things bass-ackwards to have learned being careful and accurate really does save time and effort in the long run.
My partial list of stupid mistakes: cutting a quarter inch circle off the end of one finger with a rotary cutter, using fray chek to oil a machine, cutting pieces the wrong sizes, misreading a pattern, believing that pattern instructions were always correct, intentionally sewing over pins, assembling several blocks incorrectly - even though the pieces 'went' together okay, that wasn't what I meant to do - I had forgotten how the pieces were 'supposed' to have gone together, bought too much or too little fabric, used my Gingher scissors to cut things other than fabrics, poked a hole into a piece while unsewing, forgot to look and cut more than I intended to.
That should be enough humble pie for one sitting.