You are the salt of the earth, but if salt has lost its taste, how shall its saltiness be restored? It is no longer good for anything except to be thrown out and trampled under people’s feet. (Matthew 5:13)
If salt loses its flavor, it can’t be made salty again.
If a knife loses its edge, it takes hard work to make it sharp again.
If a Christian loses his passion for God, it’s very difficult to restore that fire.
We need to be wary of anything that blunts or dulls or dampens our passion for God. It’s much easier to lose our passion for God than to restore it.