Lowering your credit limit can actually hurt your credit score. This is because it increases your overall balance to limit ratio. This means you will have a high utilization rate. This makes you look very risky to lenders, and they will be less willing to give you loans or more credit cards in the future.
This will overall hurt your credit score because your debt ratio is rise. If you are having trouble spending too much because your credit limit is so high, try to budget your money more wisely or tell yourself you will only spend a certain amount each month instead of reducing your credit card limit.