Seam allowance is the extra fabric you leave so mistakes have somewhere to go. Leave yourself a margin.

Good work plans for being slightly wrong. The extra fabric exists because your cutting will not be exact and the garment still has to fit, which is humility built into the method rather than into you. Margin is not pessimism about your skill. It is a recognition that everything real contains some error, and the error needs somewhere to go.

Add margin to one thing this week that you usually cut exactly: the time you leave, the money you hold back, the length of the first draft. Make it a little more generous than seems necessary. Notice how much less dramatic a small mistake becomes with room around it.