By this shall all men know that ye are my disciples, if ye have love one to another. ~ John 13:35
You must love the Lord your God with all your heart, all your soul, and all your mind. This is the first and greatest commandment. A second is equally important: Love your neighbor as yourself. The entire law and all the demands of the prophets are based on these two commandments. -Matthew 22: 36-40 (NLT)
The Greek word used in Galatians 5, and again here in John 13, is Agape. This is the kind of love that God loves us with - It is self-sacrificing. It is unconditional.
And, let's face it, it is impossible for any human to achieve on their own. It can only be developed as a Fruit of the Holy Spirit. But, Jesus says that developing this kind of love in your heart is the only way the world will be able to identify you as His. In Matthew, Jesus explains that Agapao (the verb form of Agape) is the actual basis of Christianity.
Consider it pure joy, my brothers, whenever you face trials of many kinds. James 1:2 (NIV)
Weeping may last through the night but joy comes with the morning. Psalms 30:5 (NLT)
There are two kinds of joy. The fleeting joy that the world gives. And the lasting joy that God's Spirit provides.
The joy that we find in this world is allusive. It is like chasing a mirage. People spend years thinking that when they finally get that promotion, or when they eventually get out of debt - they will be happy. And, yet, when they finally reach the place where they thought they would find happiness, they only experience more longing. Why? They foolishly thought that they were the source of their own joy.
But, your Heavenly Father doesn't want His child sitting around "grieved and depressed." That's why God's Word says that He's given you the very joy of the Lord to be your strength and stronghold (Nehemiah 8:10 -AMP). So, while the world is searching for happiness, the Holy Spirit is sprouting seeds of joy and gladness inside of you. And this Fruit of the Holy Spirit is God's gift, to be your strength in times of turmoil.