This is Paul and Silas... The Bible says they sang praises to God after being thrown in prison.
This is the type of joy Paul spoke about... it's not about everything being "perfect" or "easy".. but the ability to have peace during trials that would crush most people.
When you are close to God and filled with His Spirit.. you can have joy no matter what is happening around you.. even if you were unjustly thrown in prison.
So whatever Paul and Silas had that allowed them to possess this type of Joy.. THAT is the key to life.
P.S. When God saw their ability to praise even in prison... He shook open those gates and set them free.
Check it out…
But about midnight when Paul and Silas were praying and singing hymns of praise to God, and the prisoners were listening to them; 26 suddenly there was a great earthquake, so [powerful] that the very foundations of the prison were shaken and at once all the doors were opened and everyone’s chains were unfastened. 27 When the jailer, shaken out of sleep, saw the prison doors open, he drew his sword and was about to kill himself, thinking that the prisoners had escaped. 28 But Paul shouted, saying, “Do not hurt yourself, we are all here!” 29 Then the jailer called for torches and rushed in, and trembling with fear he fell down before Paul and Silas, 30 and after he brought them out [of the inner prison], he said, “Sirs, what must I do to be saved?”
The Jailer Converted
31 And they answered, “Believe in the Lord Jesus [as your personal Savior and entrust yourself to Him] and you will be saved, you and your household [if they also believe].” 32 And they spoke the word of the Lord [concerning eternal salvation through faith in Christ] to him and to all who were in his house. 33 And he took them that very hour of the night and washed their bloody wounds, and immediately he was baptized, he and all his household. 34 Then he brought them into his house and set food before them, and rejoiced greatly, since he had believed in God with his entire family [accepting with joy what had been made known to them about the Christ].
Acts 16:25-34