What does John 14:1 mean?

In the last few moments, Jesus has indicated one of the disciples is a deceiver (John 13:21) and predicted Peter will deny knowing Him at all (John 13:38; Luke 22:34). This comes in the context of frequent references to His impending death (John 12:7, 23–24).

This is why Jesus takes the time to reassure the disciples directly, telling them not to be "troubled." This comes from the same Greek root word describing Jesus' spirit in verses like John 11:33 and John 12:27. Some scholars suggest a difference between being troubled in one's spirit, as opposed to being troubled in the heart. That would suggest Jesus is not commanding anyone to "be happy," but to "be brave." Whether John intended that nuance or not, much of what Jesus is about to say involves enduring hardship without losing trust. In practice, at least, this is a call for courage more than an upbeat mood.

There is also debate over the exact meaning of Jesus' statement about belief in God and belief in Himself. This might be two individual commands: "trust God and trust Me." Or, it might be an expression of logic: "you trust God, therefore you also trust Me." Or, even as "if you trust God, you will trust Me." Given what Jesus is about to say, a double command seems to make the most sense. Regardless, it's clear that Christ is encouraging faith in God, and in Himself, in the face of what's about to come.