1.
to be extremely cautious; to look before you leap
Literally 'to tap a stone bridge before crossing it': to take great care even with something that is already safe. Usually approving, though it can suggest too much caution.
Related Words
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急がば回れ (haste makes waste)
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用心深い (cautious, careful)
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後悔先に立たず (regret comes too late)