Trust but verify: I will trust you will do X, and will do Y in return, but I will verify that you are actually doing X. Example: mutual disarmament treaties with Soviet Union, Iran nuclear deal.
Don't trust: I will not even engage with you and will not do Y. Example: the belief by some that US should not engage in high-level diplomatic talks with North Korea on disarmament because North Korea has no incentive to follow through on its promises.
Don't trust: I will not even engage with you and will not do Y. Example: the belief by some that US should not engage in high-level diplomatic talks with North Korea on disarmament because North Korea has no incentive to follow through on its promises.