"David asked HaShem, "Shall I go up to one of the cities of Judah?" And HaShem answered him, "Go up to Hebron" (Shmuel 2:2:1). After the passing of King Saul, David asked HaShem for permission to assume the kingship. HaShem instructed David, "Go up to Hebron." Why did HaShem select Hebron as the city for David to establish his kingship? Hebron is the resting place of our holy Patriarchs, Avraham, Yitzchak, and Yaacov. HaShem revealed to David that only on the merit of the Avot would his kingship succeed. David attained many significant accomplishments during his reign. He conquered the enemies of B'nei Yisrael, established Jerusalem as the capital of Israel, laid the groundwork for the building of the Temple, etc. Nevertheless, David took no credit for his successes because he was aware that all of his achievements stemmed from the exceptional merit of the Avot.
When we remember that all of our advancements arise from the merit of the Avot, we have the humility to achieve success.
Envision King David journeying to Hebron and praying at Ma'arot Machpelah, the tomb of the Avot. Sense the awe of King David when he contemplates the holiness and kindness of Avraham, Yitzchak, and Yaacov. Before each Mitzvah say this prayer, "HaShem please help me fulfill this Mitzvah on the merit of Avraham, Yitzchak, and Yaacov."
(Based on the commentary of Yalkut Mo'am Lo'ez)