When you ride with her you have to do things on her terms. If she wants to go slow you go slow. If she wants to quit after 10 miles you quit. If you don't she'll quit riding. When I know I'm going to be riding with my wife I normally go out and ride hard the day before, that way I can use my ride with her as a recovery ride.
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"You never fail, you simply produce results. Learn from these" - Anonymous