Try this
- Describe what the need changes for your choices, such as how long you can stay or how much notice you require.
- Ask about options rather than claiming your explanation automatically determines the shared plan.
A worked example
“I need to leave by nine to manage tomorrow morning. Can we start earlier, or should I join for only part of the evening?”
An invented example to adapt, not a real exchange or a script you have to follow.
Before you leave it here
A clear need can coexist with another person’s different need. If no shared option fits, separate participation may be more honest than pretending agreement.