Eating before prayer

I once heard, according to the Gemara in the blessings, that if a person said, "A psalm of the dedication of the house to David… What profit did I make with my blood? To the ruin of your soul, dust, declare your life," he can eat before praying, since he has already prayed for his blood in these verses. On the other hand, it is written later in the Gemara that there is a problem with eating before receiving the Kingdom of Heaven. Can we rely on this? Is this true? Thank you.
And Rabbi Yossi bar Hanina, on the authority of Rabbi May, says: "You shall not eat with the blood, you shall not eat until you have prayed over your blood" (14). Rabbi Yitzchak Rabbi Yochanan Rabbi Yossi bar Hanina, on the authority of Rabbi May, says: "Everyone who eats and drinks and then prays over him, as the scripture says: "And you have cast me out after your nations, you shall not call me your nations, but your nations," said the Holy One, "After he became proud, he received the kingdom of heaven upon him."