Hot water pressure is controlled by the incoming cold water to the water heater. If it is only hot water that is low pressure, you may have a blockage in the hot water piping. Could also be a partially frozen pipe, but if so, it should quickly thaw with even a small amount of flow.
If you have never made a mistake, you haven't done much.
Is your water heater old as in 8-12 years old?? It may be "calcifying" towards the bottom of the tank where the Hot water dip tube opening is inside the tank. Softened water will greatly extend the life of a water heater, but calcification eventually gets them all unless they spring leaks or have other problems.