Is Nostalgia good for our faith? Does is serve a purpose in worship or drawing us closer to God?
The Hebrews were nostalgic for the kingdom days while they were exiled in Babylon. Psalm 137 shows how the Israelites would not sing or celebrate the old days in gratitude but rather looked on them with longing. They forgot that the reason they were exiled was because of their own disobedience. Instead of learning from the exile, reflecting on how to become more righteous because of it, they only sat and wept. Furthermore, they hung up their harps and refused to sing and worship the LORD. They were trapped in the past, rather than using the current situation to move forward.
Where I most often see nostalgia present in my faith is through Worship music. When I hear certain songs (most often cheesy P&W songs that were written when I was in High School), I think back to the "good old days" when I was first really passionate about my faith, I had a very strong community that I saw many times a week, and when I was really enjoying ministry and learned what it meant to be a leader. Sometimes... I long to go back to those days, to have that type of faith.
But then I realize--God has brought me to where I am in my faith for a reason. I know what my vocation, and probably my occupation, are supposed to be. I'm more educated and able to defend and express my faith. I am ready to raise children in the faith. And I have a deeper understanding of how God works in my life through providence and grace. Those days of past faith were essential in bringing me to where I am now, but they're not where I'm meant to stay, and I should seek to grow and move forward in my faith, even if that means changing how that faith is manifest and expressed, and even if it means embracing suffering.
I think that nostalgia CAN be acceptable if one does not get trapped by it, if it doesn't preoccupy one from one's current situation, and if it motivates one to pursue correct happiness. However, it is a hard thing to do, so perhaps outside of the occasional and brief relapse, nostalgia is best avoided.