。
Don't forget to meet me tomorrow morning.
Literal
Tomorrow [possessive-の] morning me [object-に] meet [nominalizer-の] [object-を] forget-not.
A short, abrupt reminder — 忘れないで stands alone as a command without a final softening ね or ください. 会う takes its object with に (not を) — you 'meet [to] someone,' a particle quirk learners often trip over. Without ね or please, this reads as a brusque reminder.