By the Cross and Resurrection, we can Fully Know God
Until Christ faced the cross and rose from the dead, the disciples would not be able to even acknowledge it, and because of that, so much of what Jesus said and did remained a mystery to them. None of the things they (and we) need to know about God would be unknown. God would be fully made known to them - and all who would trust in Jesus. And this God who has been fully made known by Jesus would invite them to speak directly to Him as their newly adopted Father.
Take Heart: Christ has overcome the world
When Christ would rise, their deep sorrow would turn to deep and full joy. Though they (and we) would face tribulation in this world, we can take heart because Jesus overcame the world, and by faith in Him we share in His victory. This victory doesn't avoid tribulation, or even guarantee that we'll beat them - instead it guarantees something even better - that they will not rob us of our joy in God as our Father, and that for those who truly trust in Jesus, our tribulation will not cause us to turn away from God but will deepen our joy in Him. Tribulation will give way to joy in God. His resurrection secures this.