Our Lady only promised St. Bernadette happiness in the next life.
Also, I’d say that perhaps what needs to be worked on in an unhappy person’s life are the virtues. Father Benedict Groeschel has a great book about virtues.
leafletonline.com/catalog/index.php?main_page=product_info&products_id=8489
I’d also say that Hope is more closely alligned with happiness than with faith.
Also an unhappy person should pray for joy.
Here’s a couple of Bible verses that are my favorites:
Romans 12:12
Rejoice in hope, endure in affliction, persevere in prayer.
Phillipians 4-8
Rejoice 4 in the Lord always. I shall say it again: rejoice!
Your kindness 5 should be known to all. The Lord is near.
Have no anxiety at all, but in everything, by prayer and petition, with thanksgiving, make your requests known to God.
Then the peace of God that surpasses all understanding will guard your hearts and minds in Christ Jesus.
Finally, brothers, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is gracious, if there is any excellence and if there is anything worthy of praise, think about these things.