Pat is right, set is inevitable. The questions are when, where and how much. When did the set occur? Early on is a sign that something is not right. Wet or green wood for example is a set magnet. Tempering early before the damage is done can really make a difference, so long as the wood is not wet. Where? Concentrated in one spot, not good. Thats a tiller or design issue. Bending too much in one spot. Fix that and you can minimize much of the problem. Fix it early on. How much? Too much is a sign there is a problem. Again this can be caused by wet wood, poor tiller or poor design. A poor specimen can also be the culprit. It's just not good bow wood. Assuming it's dry, too narrow for the draw weight, too short for the draw length. Cant change that on this one but you can make the adjustments on the next one by realizing what occurred and making some changes on the next.
Make sure it's dry (seasoned is better), make it wider or longer, tiller for perfect shape from the first bend to the last. Temper early. These things wont eliminate set, but they will greatly reduce the amount.