Yoga of Devotion : Wisdom Stimulus 133 : Verse 12.14 : Application of Bhagvad Gita in Self Management

Lord Krishna add some more qualities of an sincere devotee

1.Contentment
2.Steady in Meditation
3.Firm Conviction
4.Self Controlled
5.Mind and Intellect dedicated to Lord Krishna

He also mentions this kind of devotee is very dear to him.