Now is your time of grief, but I will see you again and you will rejoice, and no one will take away your joy. John 16:22
Praise be to the God and Father of our Lord Jesus Christ! In his great mercy he has given us new birth into a living hope through the resurrection of Jesus Christ from the dead, and into an inheritance that can never perish, spoil or fade - kept in heaven for you, who through faith are shielded by God’s power until the coming of the salvation that is ready to be revealed in the last time. In this you greatly rejoice, though now for a little while you may have had to suffer grief in all kinds of trials. These have come so that your faith - of greater worth than gold, which perishes even though refined by fire - may be proved genuine and may result in praise, glory and honor when Jesus Christ is revealed. Though you have not seen him, you love him; and even though you do not see him now, you believe in him and are filled with an inexpressible and glorious joy, for you are receiving the goal of your faith, the salvation of your souls. 1 Pet 1:3-9
One of the over-arching themes of the New Testament is joy. It is part of God's covenant with us in Jesus and it is often contrasted with grief.
The first thing we need to be clear about is that happiness and joy are not the same thing.
Happiness is an emotion which comes and goes in dependence on circumstances while joy remains independent of circumstances.
Jesus links the disciples joy with the realisation of His resurrection. His disciple Peter, who personally experienced the grief of the death of his Lord, knew the absolute joy of seeing Him in His resurrection glory.
In 1 Peter he recognises that, even those believers who did not witness all that he did, have that inexpressible and glorious joy despite all their troubles because they have salvation.
No-one can strip us of our joy in Christ and what He has done for us.
There may be many things which make us unhappy but there is, if we are confident in our salvation, a deep sense of joy.
That joy which comes from God provides us with the strength we need to persevere through the unhappy times.
Are you finding it hard to rest in the joy of the New Covenant? The Bible writers often associate joy with the presence of God (eg 1 Chron 29:22, Ps 16:11, Ps 21:6, 1 Thes 3:9).
Spend time in prayer and in His word for in His presence is fulness of joy.