Change your needles often! Some sewists replace their sewing machine needles every time they start a new garment, others do so every other garment. Some don’t bother changing a needle unless it breaks. A good general rule is to change sewing machine needles at least every 6-8 hours of sewing time. If the fabric you are using is prone to dulling needles (e.g. polar fleece or silk) you should change your needle even more frequently. Why risk damaging your fabric with a dull needle?