Sanguine

Hopeful, confident, cheerful - the word sanguine originates from the ancient theory of the four humors or personality types. The theory went that if you had blood as your dominant bodily humor, then you were a happy-go-lucky type.  The other three humors are:

Choleric: Too much yellow bile makes you a bad-tempered hombre
Melancholic: Black bile makes you the quiet, introspective type
Phlegmatic:  An abundance of yellow bile produces a chilled out type of dude

The idea was to have a good balance of all four, which is still a good rule, I think. But in the middle ages, it lead to the idea of blood-letting as a medical treatement.