بسم الله الرحمن الرحيم
Ibn Al-Qayyim – rahimahu Allah – said:
Likewise, from among the greatest of causes that constrain the chest are turning away from Allah The Most High, attaching ones heart to others besides Him, being heedless towards remembering Him, and loving others besides Him.
For indeed whosoever loves something besides Allah, he will be agonized by it. His heart will become imprisoned by that other thing. Thus, none will exist upon earth more wretched that him, nor in a gloomier state than him, nor living a more bitter life than him, nor having a heart harder than his.
Because love is of two types:
[The first being] the love that is the paradise of [this] earth, the rejoicement of the spirt, the gratification of the heart, the bliss of the soul and it’s nourishment and cure, in fact it is its life and delight. It is love of Allah alone with all of one’s heart, and by drawing out and directing the intensities of one’s attachments, wants and love entirely towards Him.
[The second type of] love is the torment of the soul, the sadness of the spirit, the prison of the heart and the tightness of the chest. It is the cause of pain, bitterness and weariness. It is the love for other than Him – glorified be He.
Source: Ibn Al-Qayyim, Zaad Al-Ma’aad, Chapter: Concerning the causes of alleviating the chest, [of which] complete and perfect acquisition belongs to him [i.e. the Messenger] ﷺ