This is a superscription that tells about the psalm. Some scholars say that this is part of the scripture and some say that it is not. (See "What are Superscriptions in Psalms" in [Introduction to Psalms](../front/intro.md).)
These two clauses have basically the same meaning and are used together to emphasize how greatly the writer desires to be with God. Alternate translation: "my whole being greatly desires to be with you" (See: [[rc://en/ta/man/jit/figs-parallelism]])