So, the Bible says that Joy is a fruit of the Spirit. Galatians 5:22 Without the Spirit involved a person can't experience the joy of the Spirit. This isn't something that is restricted to only a certain amount of people so that no one else can get a taste of it though. It's of the Spirit, so it's not dependent on a certain thing to "happen". It's not "happiness" because happiness depends on what "happens". Joy has more substance than that. It's a fruit of the Spirit. When a person believes on Jesus, and repents from sin, they can also taste the joy of the Spirit. Because when they believed in Christ He identified them as His own by giving them the Holy Spirit. So, when a person has the Spirit they can taste the joy of being saved. The joy in having their sins wiped clean and made new. The joy of knowing that trials or tribulations aren't the end but forever in Heaven is. A beautiful and glorious place..
13 And now you Gentiles have also heard the truth, the Good News that God saves you. And when you believed in Christ, he identified you as his own by giving you the Holy Spirit, whom he promised long ago. 14 The Spirit is God’s guarantee that he will give us the inheritance he promised and that he has purchased us to be his own people. He did this so we would praise and glorify him.
So, don't let satan steal the joy of your salvation. The Spirit of God given to us is God's "guarantee!" that He will give us, as believers, salvation. So, if something has been going on and it's been overwhelming you then take some breathers from what's been going on around you and know that God is God and you are His child. He is faithful and He as a purpose even after all that you've been going through. Have faith, trust God's will for your life, remain faithful, and love others..
But if you decide to go against God's law one time don't let satan steal your joy by beating yourself down. Confess the sin, forsake it, and get into prayer as to why you did, and ask God to refine your heart in that area. Don't just beat yourself down with, "You call yourself a christian? Come on! Be real with yourself". The Christian walk has ups and downs. Peter denied Jesus three times when he promised that he wouldn't deny Him. Matthew 26, Mark 14 And what happened after that? Jesus forgives him and tells him to feed His sheep. John 21:17 Forgiving is as easy as drinking as glass of water for Jesus. Just don't let your shame keep you from obtaining forgiveness..
So, when you come to a down, whether it be sin, a problem with a certain relationship, gossip from a close friend, or a tragic thing that happened, then take the promises of God's word and take refuge in them. If you need to apply the confessing to your sins then apply it and get back to living in peace. Get back to enjoying joy of your salvation..