A person's deepest longing is often directed toward connection and purpose. Recognizing that God is his ultimate hope and true portion [רש״י], the psalmist turns all his desires toward Him. Rather than asking for anything in this physical world, he seeks only the closeness of God [מלבי״ם]. This profound yearning is expressed as an intense plea to experience God's presence directly [מצודת ציון, ביאור שטיינזלץ].
This plea is made with complete willingness and total devotion [ביאור שטיינזלץ]. Such full-hearted commitment means channeling every aspect of oneself toward serving God. This level of dedication can even include harnessing one's negative impulses and redirecting them entirely toward a spiritual purpose [אלשיך].
Approaching God with such intensity requires profound humility. The psalmist understands that no matter how devoted he might be, his own righteous actions are never enough to earn a reward. Knowing he lacks the personal merit to make demands, he begs instead for unearned kindness and free grace [אלשיך, ביאור שטיינזלץ].
Because he cannot rely on his own standing, he bases his request entirely on a prior divine promise [מאירי]. The primary approach among commentators is that this refers to God's ancient assurance to Moses, where He promised to grant grace even to those who are unworthy [רד״ק, אבן עזרא, אלשיך]. Other perspectives suggest that the plea relies on a more specific guarantee, such as the message God sent to David through Nathan the prophet [מצודת דוד], or the general promise that God will remain the devoted person's eternal portion [מלבי״ם].