A ship in port is safe; but that is not what ships are built for. Sail out to sea and do new things.

This saying appears to be due to John Augustus Shedd; it was quoted in "Grace Hopper : The Youthful Teacher of Us All" by Henry S. Tropp in Abacus Vol. 2, Issue 1 (Fall 1984) ISSN 0724-6722 . She did repeat this saying on multiple occasions, but she called it "a motto that has stuck with me" and did not claim coinage. Additional variations and citations may be found at Quote Investigator