Passage
And ye also shall bear witness, because ye have been with me from the beginning.
And ye also shall bear witness, because ye have been with me from the beginning.
John 15:25 But this cometh to pass, that the word might be fulfilled that is written in their law, They hated me without a cause.
John 15:26 But when the Comforter is come, whom I will send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me:
John 15:27 And ye also shall bear witness, because ye have been with me from the beginning.
The verse centers on "shall", "bear", "witness", "been", and "beginning". It is saying that the verse draws attention to "shall" and "bear", so its meaning should be read from those terms before moving to application.
The prior verse says "But when the Comforter is come whom...", giving immediate footing for "shall" and "bear". 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 "shall" and "bear" with trust shaped by these words, not by a vague optimism outside the passage.