It's not luck it's experience. Stick with it. Also, as you experienced, meats will continue to rise in temperature by a significant amount after you take them out of the oven, so you should factor that into your calculation. I only use thermometers for slow cooking on a barbecue (where I can't be sure of the temperature I am cooking at) and even then only for stuff you wouldn't want to eat underdone (chicken, turkey). Other than that timecharts and experience with the time / temperature works for me. Becoming overly dependent on thermometers prevents you from developing this experience.