This poem by Richard Lovelace is a brief lyric from a lover saying goodbye to his partner as he has to go to the war.
The rhyme scheme in the provided excerpt can be determined by checking the end-word in each line. Style-wise, this very simple poem comprises of just three stanzas, each having four lines.
However, the question asks about the set rhyme scheme utilized in the excerpt. So, the rhyme follows the underlying pattern:
Scheme 'ABAB', which can be further elaborated as, rhyme 'A' for "unkind" and "mind" and 'B' for "nunnery" and "fly".