The relationship between a devotee and his God is sacred and only the devotee and his / her God will know the truthfulness. External signs can be false and misleading but we cannot deceive the God who dwells in our heart. Thus we may put on all the external symbols like Vibhuti, Rudraksha, Kumkum or many other marks to show that we are devoted, but what counts is our mind and heart. We can't pretend to our conscience. Since Sri Sai is SATCHITANANDA, SAT means TRUTH. He knows whether our devotion to him is true or not.
During times of difficulty, do we remember him and pray to him? After all the prayers, do we accept the results as his will especially if the result is not what we prayed for? If yes, we can say we are true devotees. It is a very difficult test indeed and though we may pass it once or twice we may not pass it all the time. In fact getting a steadfast devotion to any God is itself due to God's or Guru's grace.
So let us pray to Sri Sai to give us true steadfast devotion.