There are easy ways to stop drafts in your home. These photos show a range of places where air typically finds an easy way to draft into your home. Any cracks or holes through the walls, floor or ceiling of your home are offering easy access for air to infiltrate your home. Seal these up with caulk or expanding foam (eg: Great Stuff) to help reduce drafts in your home. When sealing walls, if you can, seal them up from the outside to stop air from getting into your wall cavities.
if a mouse can get in your home, then air can too
look how much air can leak around this floor register
plumbing access under the tub should be air sealed
large opening under your tub means cold air in your bathroom
door weatherstrip doesn't do much if it doesn't seal against the door
This attic hatch needs to be properly air-sealed
water damage under a sink means air leakage
If you can see daylight around your door, you need weatherstrip
big air leak here!
An old unused pet door should be fully removed and air sealed