How is true Christian zeal different from false zeal?

This article on Romans 12:11 is about indifference and zeal in our service to the Lord.

The Lord's Supper is so beneficial to us, since it gives us grace. We receive grace in Jesus Christ, and through the Lord's Supper experience hope, zeal and unity.

In this article about motives in the mission work, the author also looks at church growth, missions and the glory of God, missions and the salvation of man, and the conviction and zeal for mission work.

This article is about the eagerness and zeal to teach.

Is it right that we should feel guilty when we do not always have the right affection and love and zeal towards God? This article is about spiritual dullness and spiritual vigour.