Hi @awosode. I find it very difficult to discern why other people serve God. The only heart I can see is my own and that is the heart I must guard. Sometimes I struggle to see clearly into my own heart's motives and I need to make sure I see all there is to see.
David prayed this prayer and I think we should all pray it often.
Search me, O God, and know my heart; test me and know my anxious thoughts. Point out anything in me that offends you, and lead me along the path of everlasting life.
Psa 139:23-24 NLT