have a mind of one's own
To be strong-willed and independent, unwilling to be persuaded or dissuaded by others
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Main Entry: ↑mind
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be capable of independent opinion or action
■ (of an inanimate object) seem capable of thought and intention, esp. by behaving contrary to the will of the person using it
the shopping cart had a mind of its own
Useful english dictionary. 2012.