Passage
And I am glad, for your sakes; that I was not there, that you may believe. But, let us go to him.
John 11:15 (DRB)
Nearby Context
John 11:13 But Jesus spoke of his death: and they thought that he spoke of the repose of sleep.
John 11:14 Then therefore Jesus said to them plainly: Lazarus is dead.
John 11:15 And I am glad, for your sakes; that I was not there, that you may believe. But, let us go to him.
John 11:16 Thomas therefore, who is called Didymus, said to his fellow disciples: Let us also go, that we may die with him.
John 11:17 Jesus therefore came: and found that he had been four days already in the grave.
Study Lenses
The verse centers on "glad", "sakes", and "believe". It is saying that the verse draws attention to "glad" and "sakes", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 14's "Then therefore Jesus said to them plainly..." into verse 16's "Thomas therefore who is called Didymus said...", so "glad" and "sakes" 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 "glad" and "sakes" with trust shaped by these words, not by a vague optimism outside the passage.