> The story goes tariffs only hurt yourself

That's how the story goes with someplace like China. If you impose tariffs on imports you have no cost-effective alternative for, yes, the tariffs will only hurt the importer, because buying habits will not change. (I suppose Chinese cars are a big exception here)

But in this case, the math is probably different because none of these tariffs affect products the US must realistically buy from Canada (e.g. oil and potash). So Canadian exporters will feel some pain and American importers will feel some pain.

What should Canada do in this case if the two can't come to a trade agreement? Continue to import from the US at the same rate as before?