Similar to how the law let's us know sin, the spirit let's us know fruitfulness. These fruits nourish us in our times of need and to share with those who're in need. Interesting how love is listed first among the fruits of the Spirit, just as it's something we have with God, all are with Him and in the Lord as we have been loved are in return given to each other. (John 15:9, John 15:11, John 15:26-27)
Those happy feelings do give hope, helps to remind me of how God has been there for me and all I need is a little faith to believe He's there and not gone. The mindset we have does make the difference and when we remember Him, it does occupy what otherwise would been negativity. Even if you're not very fruitful or feeling in the spirit, what you had helps you stay positive until you're able to be renewed spiritually. Me too, I'm thankful for God and how merciful He's been to us. Not only judgment and forgiveness, but when people suffer He's compassionate and does for us.