I rationalize it this way: I have a yellow gold ring with white diamonds on it. But I have a stainless steel watch. But hey, the face of the watch is white and so are the diamonds. Presto! They match.
I have a gold ring with a brown diamond. I have a stainless steel watch (same watch). It has a brown band. The brown band matches the brown diamond. Presto! They match.
Maybe start looking at the pieces for the colors they contain and not just at the metals--you'll get way more wear out of your pieces if you can find a way to be comfortable mixing metals.
So for example. Navy and orange can work well together. I can see your cute new bag with a French sailor stripe shirt--those ones with the blue stripes. Since that has blue in it, work with that in your jewelry. Do you have yellow gold with sapphire? That would work for earrings with your two tone watch, no problem.
The watch is near your bag, so the white metal on the watch, would match the hardware.
Mostly, just remember that there really isn't a "Fashion Police" that will come bust you for not getting your metals right and use that idea as a lighthearted reminder to try the small risk.
Just try it. You will not meet any harm in mixing metals, just keep the tone the same.
Tone meaning, no super thin gold bracelet with big chunky silver bracelet at the same time...but chunky silver bracelet and chunky gold bracelet, why not?