Passage
In that day you shall know that I am in my Father: and you in me, and I in you.
John 14:20 (DRB)
Nearby Context
John 14:18 I will not leave you orphans: I will come to you.
John 14:19 Yet a little while and the world seeth me no more. But you see me: because I live, and you shall live.
John 14:20 In that day you shall know that I am in my Father: and you in me, and I in you.
John 14:21 He that hath my commandments and keepeth them; he it is that loveth me. And he that loveth me shall be loved of my Father: and I will love him and will manifest myself to him.
John 14:22 Judas saith to him, not the Iscariot: Lord, how is it that thou wilt manifest thyself to us, and not to the world?
Study Lenses
The verse centers on "shall" and "father". It is saying that the verse draws attention to "shall" and "father", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 19's "Yet a little while and the world..." into verse 21's "He that hath my commandments and keepeth...", so "shall" and "father" 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 "shall" and "father" with trust shaped by these words, not by a vague optimism outside the passage.