How to fix a cross stitch mistake (and when to leave it)
Unpicking is called frogging, because you rip it, rip it. It is part of the craft, not a failure.
Find out how far back it goes
Before removing anything, count from the nearest heavy grid line on the chart to the matching line on the fabric. A miscount by one square shifts everything stitched after it. A wrong colour in the right place is a smaller problem: only those stitches come out.
Unpicking
Turn the work over and use the needle tip, or a small blunt seam ripper, to lift the back stitches one at a time. Never cut from the front: aida threads are easy to nick, and a cut block is nearly impossible to hide. Pull out the loose floss and discard it; unpicked floss is fuzzed and should not be reused.
When to leave it
A single stitch in a slightly wrong shade of the same colour, inside a block of that colour, will never be seen. A stitch one square out along an outline will. The test is whether it changes a shape, not whether it exists.
