As Shivani Devi stated, it is the attitude of divine love.
It is the easiest way to effect concentration of the mind on the divine through the aid of emotion, enabling purification of the mind.
Good music, company of devotees, devotional literature all are aids to help one attain the attitude of divine love.
Adherence to
yama-niyamas is also essential to ensure that any kundalini rises as a result of devotional love, is channeled properly without any issues.