Always attack your own ideas as hard as you can. Ask yourself what evidence you have for what you believe is true. Figure out possible facts that will prove your idea false. Seek out evidence for those contrarian facts. Be ready to drop precious ideas that turn out to be brittle against facts.

Any test for determining whether I’m doing a “good job” at dropping ideas that contradict evidence?

How often have you dropped an idea you think is true after attacking it with everything you have? If it never happens then it is likely that you are not doing a “good job”. If few ideas you like/agree with survive then you are more likely to be doing a “good job”. It is humbling for me to realise how quickly I can emotionally believe something to be true and then realise that I have no real evidence to support it. And remembering all the things I used to think was true and I now realise might not be (not enough conclusive evidence). The key insight is that ideas are just models of the world. All flawed and with the potential to be improved/more accurate. Don’t become your ideas. Stand apart from your ideas/truths and be critical of them. Assume you are wrong and try to prove it.