There is no limit, the only condition is sincerity. Let me explain with an example. Every Muslim reads 'Alhamdulillah' every day in the prayer but I have not found a single person who utilised his mind to understand its meaning.

I used my mind and understood that if I want to express my gratitude to God, then how a big thanksgiving will emerge when so many negative experiences come my way every day. Amidst these experiences, how will I thank God?

I realised that "Alhamdulillah" invites an entire culture to forget those things that lead one to negativity. There is no one in the world that does not undergo negative experiences. Everyone lives in the psyche of complaints. In such a scenario, how will he render big thanks to God unless he adopts this culture! He will have to forget negative emotions, hatred and losses so that he is able to thank God. Bernard Shaw said that, 'The most uneducated man is one who has nothing to forget!" I would say that to be able to thank God, you will have to forget! If I would not have used my mind, I would not have understood this meaning. I realised that 'Alhamdulillah' is a killer of all kinds of complaints, negative emotions and feelings. And when man prays as such, he will become a new person, devoid of negativity and hatred because he would realise that unless he purifies himself he will not be able to say true, 'Alhamdulillah'!

Source: The Seeker’s Guide