John 6:44 was spoken by Jesus to a group of men who never came to Jesus as the bread of life sent from the Father. They never ate his flesh and drank his blood and they did not have everlasting life in them because of their unbelief. The Father said in his word concerning the manna, that he will provide it from heaven so you may live by eating it, but it is the manna that gives life when it is in you.
That is how simple this is. Jesus said in the text that unless you eat my flesh and drink my blood you have no life in you. How simple is this. These unbelievers came to the son, but they did not eat him.
Jn 6:52 The Jews therefore strove among themselves, saying, How can this man give us [his] flesh to eat?
53 Then Jesus said unto them, Verily, verily, I say unto you, Except ye eat the flesh of the Son of man, and drink his blood, ye have no life in you.
54 Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day.
55 For my flesh is meat indeed, and my blood is drink indeed.
56 He that eateth my flesh, and drinketh my blood, dwelleth in me, and I in him.
57 As the living Father hath sent me, and I live by the Father: so he that eateth me, even he shall live by me.
58 This is that bread which came down from heaven: not as your fathers did eat manna, and are dead: he that eateth of this bread shall live for ever.
59 These things said he in the synagogue, as he taught in Capernaum.
1 Jn 5:9 If we receive the witness of men, the witness of God is greater: for this is the witness of God which he hath testified of his Son.
10 ¶ He that believeth on the Son of God hath the witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son.
11 And this is the record, that God hath given to us eternal life, and this life is in his Son.
12 He that hath the Son hath life; [and] he that hath not the Son of God hath not life.
13 These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God.
14 And this is the confidence that we have in him, that, if we ask any thing according to his will, he heareth us:
That is how simple this is. Jesus said in the text that unless you eat my flesh and drink my blood you have no life in you. How simple is this. These unbelievers came to the son, but they did not eat him.
Jn 6:52 The Jews therefore strove among themselves, saying, How can this man give us [his] flesh to eat?
53 Then Jesus said unto them, Verily, verily, I say unto you, Except ye eat the flesh of the Son of man, and drink his blood, ye have no life in you.
54 Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day.
55 For my flesh is meat indeed, and my blood is drink indeed.
56 He that eateth my flesh, and drinketh my blood, dwelleth in me, and I in him.
57 As the living Father hath sent me, and I live by the Father: so he that eateth me, even he shall live by me.
58 This is that bread which came down from heaven: not as your fathers did eat manna, and are dead: he that eateth of this bread shall live for ever.
59 These things said he in the synagogue, as he taught in Capernaum.
1 Jn 5:9 If we receive the witness of men, the witness of God is greater: for this is the witness of God which he hath testified of his Son.
10 ¶ He that believeth on the Son of God hath the witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son.
11 And this is the record, that God hath given to us eternal life, and this life is in his Son.
12 He that hath the Son hath life; [and] he that hath not the Son of God hath not life.
13 These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life, and that ye may believe on the name of the Son of God.
14 And this is the confidence that we have in him, that, if we ask any thing according to his will, he heareth us: