The idea that you can only have joy when things are going good is just not true. Have you ever been in a poor country where you see children playing that have no shoes in total poverty. Joy is a gift from God. It's a matter how you look at life itself. If your focus is on attaining things and money, you will not have much joy in your life. If on the other hand you put your focus first on God, he promises to provide joy even when things are not so great.
We all have to evaluate our focus all the time. Even as Christians, we can lose our focus, however, our joy is just a prayer away.
This is the day the LORD has made; We will rejoice and be glad in it. Psalms 118:24 (NKJV)
For His anger is but for a moment, His favor is for life; Weeping may endure for a night, But joy comes in the morning. Psalms 30:5 (NKJV)
You have turned for me my mourning into dancing; You have put off my sackcloth and clothed me with gladness, Psalms 30:11 (NKJV)
For our heart shall rejoice in Him, Because we have trusted in His holy name. Psalms 33:21 (NKJV)
The righteous shall be glad in the LORD, and trust in Him. And all the upright in heart shall glory. Psalms 64:10 (NKJV)
But let the righteous be glad; Let them rejoice before God; Yes, let them rejoice exceedingly. Psalms 68:3 (NKJV)
Blessed are the people who know the joyful sound! They walk, O LORD, in the light of Your countenance. In Your name they rejoice all day long, And in Your righteousness they are exalted. Psalms 89:15-16 (NKJV)
Light is sown for the righteous, And gladness for the upright in heart. Rejoice in the LORD, you righteous, And give thanks at the remembrance of His holy name. Psalms 97:11-12 (NKJV)
"As the Father loved Me, I also have loved you; abide in My love. "If you keep My commandments, you will abide in My love, just as I have kept My Father's commandments and abide in His love. "These things I have spoken to you, that My joy may remain in you, and that your joy may be full. John 15:9-11 (NKJV)
For the kingdom of God is not eating and drinking, but righteousness and peace and joy in the Holy Spirit. For he who serves Christ in these things is acceptable to God and approved by men. Romans 14:17-18 (NKJV)
Rejoice in the Lord always. Again I will say, rejoice! Let your gentleness be known to all men. The Lord is at hand. Be anxious for nothing, but in everything by prayer and supplication, with thanksgiving, let your requests be made known to God; and the peace of God, which surpasses all understanding, will guard your hearts and minds through Christ Jesus. Philippians 4:4-7 (NKJV)
Through whom also we have access by faith into this grace in which we stand, and rejoice in hope of the glory of God. And not only that, but we also glory in tribulations, knowing that tribulation produces perseverance; and perseverance, character; and character, hope. Romans 5:2-4 (NKJV)