When candidates vyed for public office in Rome, they walked around the city, urging people to vote for them. The word for this was ambitio, which comes from ambire (to go around).
This ritual gave rise to the word ambition, which came to mean ‘the desire for honour or power’. From its very roots, ambition is rooted on how we are perceived by others. It is a desire for status, approval and approbation of other people. An ambitious person may seek excellence, but it is as a means to another end.
Excellence is doing something well for its own sake. It is the pursuit of achievement, calibre, perfection and mastery because of the joy derived from this pursuit itself. While ambition is a means to an external end, excellence is intrisinc.
We are driven by ambition to gain the approval of others. We strive to excel even when nobody else is watching.