There is no difference between Sri Krishna Prasad and Lord Sri Krishna. Prasad is a Sanskrit word which means mercy. So Sri Krishna Prasad is Lord Sri Krishna’s special mercy upon us. By having Sri Krishna Prasad our consciousness will become pure and we will be able to progress in spiritual life.
Before having prasad we should chant the following mantras and pray for Lord’s mercy.
"O king, for those who have done very few pious activities, their faith in maha-prasada, in Shri Govinda, in the Holy Name and in the Vaisnava is never born."
Sarira abidya-jal, jodendriya tahekal,
jibe phele bisaya-sagore
taar madhye jihva ati, lobhamoy sudurmati
take jeta kathina somsare
krsna baro doyamoy, karibare jihva jay,
sei annamrta Pao, radha-krsna-gunagao,
preme dako caitanya-nitai
Jai Nimai Jai Nitai
Jai Shri Krishna Chaitanya
Sri Advaita Gadhadhara
Srivasadi Gaur Bhaktvrinda
Hare Krishna Hare Krishna Krishna Krishna Hare Hare
Hare Ram Hare Ram Ram Ram Hare Hare
"This material body is a place of ignorance, and the senses are a network of paths to death. The senses throw the soul into this ocean of material sense enjoyment and, of all the senses, the tongue is most voracious and uncontrollable; it is very difficult to conquer the tongue in this world. O brothers! Lord Krishna is very kind to us and has given us such nice prasada, just to control the tongue. Now let us take this prasada to our full satisfaction and glorify Their Lordships, Shri Shri Radha and Krishna and, in love, call for the help of Lord Chaitanya and Prabhu Nityananda."