Assalaamu 'alaykum.
It was narrated that Abu Hurairah said:
"The Messenger of Allah (ﷺ) said: 'The strong believer is better and more beloved to Allah than the weak believer, although both are good. Strive for that which will benefit you, seek the help of Allah, and do not feel helpless. If anything befalls you, do not say, "if only I had done such and such" rather say "Qaddara Allahu wa ma sha'a fa'ala (Allah has decreed and whatever he wills, He does)." For (saying) 'If' opens (the door) to the deeds of Satan.'"
[Sunan Ibn Majah]
"No amount of guilt can change the past and no amount of worrying can change the future. Go easy on yourself for the outcome of all affairs is determined by Allah's Decree. If something is meant to go elsewhere, it will never come on your way, but if it is yours by destiny, from you it cannot flee.''
['Umar ibn al-Khattab]
Ali bin Abi Talib رضي الله عنه went to Ash'ath to console him upon the death of one of his sons. He said:
"If you are sad, then you are deserving of mercy, but if you are patient, then Allah gives you something in place of what was lost or destroyed. And know that if you are patient, everything that was described for you and preordained for you will occur and you will be rewarded. If you complain and are hopeless, then likewise all that was destined for you will occur, except that you will be blamed for your impatience at Allah's will."
[Gems and Jewels, Abdul Malik Mujahid]
May Allah ta'ala bless you with success in the dunya and the aakhirah, and may His rahmah and barakah be upon you. May He ease for you your task and put your mind and heart at ease.