Dogs can quite literally smell fear,.. and when they know you are scared they take advantage of it. My personal approach is "Kick first, ask questions later" if a dog is trying to injure me, and I have zero hangups about it.
Starting with that attitude means I have very little problems with even the bigger dogs,.. if a dog even so much as growls at me I growl back and make a run for them,... they ALWAYS back off from an unexpected attack, and quickly learn who is the boss. Dogs have a pack mentality,.. let them think they're the boss at the start and you are asking for trouble.
Still, big dogs and dogs in packs can be dangerous,.. if you're not confident, best avoid the house all together.