Note 2 at Jn. 14:1: The understood subject of this sentence is "you." "You" let not your heart be troubled. We are the ones who have control of our hearts. Other people and circumstances cannot trouble us unless we allow them to divert our attention from the Lord and His Word (Isa. 26:3; see note 39 at Jn. 14:27, p. 434).

Note 3 at Jn. 14:1: Jesus had just told them not to let their hearts be troubled and now He tells them how to do it. Believe! Faith in God is the victory that overcomes the world and all its troubles (1 Jn. 5:4).

Note 4 at Jn. 14:1: The disciples believed in Jesus enough to be totally devastated when Jesus died, but not enough to believe His prophecies concerning His resurrection (see note 1 at Mt. 16:21, p. 202). Jesus made it very clear in this same teaching (Jn. 16:1) that He was saying these things so His disciples would not be offended, but His words didn't profit them because they didn't mix them with faith (Heb. 4:2).

They had enough faith to be dissatisfied with failure but not enough to have victory. It's better to go all the way in believing God than just part way.