You’re right about everything so yes, I suppose it’s ironic. Maybe it means ‘One day I’ll take the decision to never see you again so if we meet in the future, it will be by chance’.

Cette contradiction est un procédé rhétorique appelé antilogie, la plupart du temps utilisé pour produire un effet comique ou poétique.

Such a contraction is a rhetoric formula called antilogy, usually used to create a comic or poetic effect.