Does frequent intercourse affect the faith in one's heart, thereby diminishing it and opening the door to lust, and what is the guidance for rectifying the heart in a way that pleases Allah?

Legitimate intercourse helps purify the heart. Therefore, the Prophet (peace and blessings be upon him) commanded intercourse when one's soul inclines towards a woman. However, excessive intercourse can be detrimental to health. Thus, one should respond to the call of intercourse when there is a need for chastity, while being cautious of what harms health. The Prophet (peace and blessings be upon him) forbade abandoning women, and Ibn Abbas said: "Marry, for the best of this Ummah are those who have the most women."