carefully, because you think there may be a danger or problem or you do not trust somebody/something 谨慎：小心，因为您认为可能存在危险或问题，或者您不谨慎地信任某人/某事（1）
Idioms
tread carefully, warily, etc.
to be very careful about what you do or say 小心谨慎地说；小心翼翼地做 The government will have to tread very carefully in handling this issue. 政府在处理这个问题时须慎之又慎。 We must tread warily —we don't want to offend anyone. 我们必须小心行事——我们不想得罪任何人。