Be courteous to all, but intimate with few, and let those few be well tried before you give them your confidence. True friendship is a plant of slow growth, and must undergo and withstand the shocks of adversity before it is entitled to the appellation.
Source: Letter, 15 Jan. 1783.
-- George Washington, (Feb 22 1732-1799), US president (1st), soldier, surveyor, farmer; He was Commander of the Continental forces; as U.S. president he shaped the office and warned against party politics.