The infinitive phrase plays the role of an adverb in this sentence. It tells why you met at the park. In the sentence "You met at the park to run", "to run" is the infinitive phrase.
adjective
"to be persistent" is the subject.
adverb
predicate nominative
adverb
Adverb
adverb
adjective
adjective
adjective
adjective
adverb
adverb
"to be persistent" is the subject.
adverb
"to be persistent" is the subject.
adverb