Every discount comes straight out of your margin. See how much extra volume a price cut really demands — before you approve it.
Required volume increase = discount ÷ (margin − discount). At 40% margin, a 10% discount leaves 30 points of margin per unit instead of 40 — so you need 40/30 = 1.33× the volume (+33%) for the same gross profit. If the discount ≥ your margin, no volume can save you: you lose money on every sale.