One of the most used words by Muslims is Alhamdulilah, which means All praise to Allah or put even more simply: Thank God.
Alhamdulilah is probably one of the words converts learn first too. It has the advantage of being comparatively easy to pronounce and it can be used in many situations.
There is something very satisfying about saying Alhamdulilah, it's phonetics are soothing, to say it is like exhaling deeply.
As well as a word of praise, it's one of reassurance and remembrance.
Alhamdulilah. Thank You. For all the blessings I remember, for all the blessings I forget and more importantly, I thank You for Your existance, for Your Light and Guidance. Your perfection and permanance beyond my understanding as well as the beauty of Your creation that I can witness and experience.
All praise is due to You. Ameen