If you’re not coming, say so. Ghosting a plan is lying with silence.

Saying nothing feels passive and functions as a statement, because the other person is still operating on the last thing they heard. They keep the evening free, they wait, and eventually they work out that the answer was no and that you let them find it themselves. Silence is not a gentler way of declining, it is declining while making somebody else do the work of understanding it.

Send the message, even late: one line saying you cannot make it. If you have gone quiet on something already, name it rather than hoping it faded. People forgive a cancellation and remember being left to guess.