Choose a workable moment
Avoid beginning a serious conversation when either person is rushing, intoxicated, or already in a heated argument. Ask for a time when you can both pay attention.
Speak from your experience
“I felt alone when plans changed without telling me” gives the other person something concrete to respond to. It is often easier to hear than a broad judgement about their character.
Know your boundary
Before you begin, decide what you will do if the conversation becomes insulting, threatening, or unsafe. You can pause it and seek support.