Lord Krishna explains the importance of remembering Him always:

yam yam vapi smaran bhavam
tyajaty ante kalevaram
tam tam evaiti kaunteya
sada tad-bhava-bhavitah

tasmat sarveshu kaleshu
mam anusmara yudhya cha
mayy arpita-mano-buddhir
mam evaishyasy asamshayah

"Whatever state of being one remembers when he quits his body, O son of Kunti, that state he will attain without fail. Therefore, Arjuna, you should always think of Me in the form of Krishna and at the same time carry out your prescribed duty of fighting. With your activities dedicated to Me and your mind and intelligence fixed on Me, you will attain Me without doubt."

At the time of death, our state of consciousness determines our next birth. Death destroys the body made up of the five gross elements, but the subtle body, consisting of mind, intelligence, and false ego, remains. As the air carries the scent of the place it blows over, so the soul carries a person's subtle body of mind, intelligence, and false ego, along with his state of consciousness, on to his next birth, and his body is determined accordingly. When a breeze blows over a garden, it carries the fragrance of flowers with it, but when it blows over a rubbish heap, the breeze is filled with the stench. Similarly, the activities a person performs during his lifetime continuously influence his mentality, and at the time of death the cumulative effect of these activities determines his state of consciousness. Thus the subtle body formed during one's lifetime is carried over to one's next birth and manifests as the soul's next gross body. Naturally, therefore, the gross body reflects one's state of consciousness. As the popular saying goes, "The face is the index of the mind." And the mind is the product of the activities of one's present and previous lives. In other words, one's mind, intelligence, and false ego, which are influenced by one's habits in this and previous births, form the matrix that determines the type of body and mentality one will have in the next life. Hence the connection between one's previous, present, and future lives is the mind, intelligence, and false ego.

The activities of the day evoke dreams at night and induce emotions appropriate to those activities. Similarly, the activities performed in one's lifetime flash across one's mind at the moment of death and determine one's next life. Therefore, if one's present activities are directed toward chanting, hearing, and remembering the Supreme Lord's transcendental name, along with descriptions of His beauty, qualities, pastimes, associates, and paraphernalia, then one's consciousness at the moment one leaves his body will automatically be attracted to the Lord. Such a spiritual state of consciousness at the moment of death ensures the soul entry into the Supreme Lord's eternal abode in his very next birth. To awaken this spiritual consciousness is man's prime goal in life. We therefore find that Lord Krishna, out of compassion for the conditioned souls, instructs Arjuna to fight and at the same time remember Him. This is called karma-yoga. Therefore devotees always remember Him in all their activities—in their endeavors for food and safety and even in the middle of the battlefield while fighting a war. Life being like a battlefield, in which one may die at any time, the devotees remember Him at every moment, and He willingly becomes the charioteer of their chariotlike bodies. The activities of their bodies, minds, and words are thus prompted by the Supreme Lord's will, and at the end, when they leave their gross and subtle bodies, they go directly to the spiritual sky.