Passage
but ye do not believe, for ye are not of my sheep,
but ye do not believe, for ye are not of my sheep,
John 10:24 the Jews, therefore, came round about him, and said to him, `Till when our soul dost thou hold in suspense? if thou art the Christ, tell us freely.'
John 10:25 Jesus answered them, `I told you, and ye do not believe; the works that I do in the name of my Father, these testify concerning me;
John 10:26 but ye do not believe, for ye are not of my sheep,
John 10:27 according as I said to you: My sheep my voice do hear, and I know them, and they follow me,
John 10:28 and life age-during I give to them, and they shall not perish--to the age, and no one shall pluck them out of my hand;
The verse centers on "sheep" and "believe". It is saying that the verse draws attention to "sheep" and "believe", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 25's "Jesus answered them I told you and..." into verse 27's "according as I said to you My...", so "sheep" and "believe" belong inside that flow. In John context, the local focus is the identity of Jesus, new birth, eternal life, and belief and unbelief.
A plain takeaway is to answer the verse's own emphasis on "sheep" and "believe" with trust shaped by these words, not by a vague optimism outside the passage.