Dua is a very powerful tool for a believer that not only does it remove existing calamities, it also prevents future difficulties.
Prophet Muhammad (peace and blessings of Allah be upon him) : “The supplication is the essence of worship.”
Jami` at-Tirmidhi
“النَّبِيِّ صلى الله عليه وسلم قَالَ “ الدُّعَاءُ مُخُّ الْعِبَادَةِ
Here are some beautiful duas from the Sunnah
O Allah! I seek refuge in You from helplessness, indolence, cowardice, senility, and miserliness; and I seek Your Protection against the torment of the grave and the trials of life and death.
Muslim
اللهم إني أعوذ بك من العجز والكسل والجبن والهرم، والبخل، وأعوذ بك من عذاب القبر، وأعوذ بك من فتنة المحيا والممات.
Allah! I have considerably wronged myself. There is none to forgive the sins but You. So grant me pardon and have mercy on me. You are the Most Forgiving, the Most Compassionate
Al Bukhari
اللهم إني ظلمت نفسي ظلمًا كثيرًا، ولا يغفر الذنوب إلا أنت، فاغفر لي مغفرة من عندك، وارحمني، إنك أنت الغفور الرحيم
O Allah! I seek refuge in You from leucoderma, insanity, leprosy and evil diseases
Abu Dawud
اللهم إني أعوذ بك من البرص والجنون، والجذام، وسيئ الأسقام
O Controller of the hearts make my heart steadfast in Your religion
Tirmidhi
يا مقلب القلوب ثبت قلبي على دينك
None has the right to be worshipped but Allah the Incomparably Great, the Compassionate. None has the right to be worshipped but Allah the Rubb of the Mighty Throne. None has the right to be worshipped but Allah the Rubb of the heavens, the Rubb of the earth, and the Rubb of the Honourable Throne
لا إله إلا الله العظيم الحليم، لا إله إلا الله رب العرش العظيم، لا إله إلا الله رب السماوات ورب الأرض ورب العرش الكريم