Praise be to Allah.
Difficulty in working, in which a person feels that he is not doing his job properly, is not one of the excuses that makes it permissible not to observe an obligatory fast and move to the option of feeding the poor, whether it is fasting during Ramadan, fasting in expiation for having intercourse during the day in Ramadan, or fasting for any other reason.
The Standing Committee for Issuing Fatwas was asked about a man who works in a bakery and suffers extreme thirst and exhaustion whilst working. Is it permissible for him not to fast?
They replied: It is not permissible for that man not to fast; rather what he must do is observe the fast. The fact that he is baking during the day in Ramadan is not an excuse for not fasting. He must work according to what he is able to do.
End quote from Fataawa al-Lajnah ad-Daa’imah lil-Buhooth al-‘Ilmiyyah wa’l-Iftaa’ (10/238).
We put this question to our shaykh, ‘Abd ar-Rahmaan ibn Naasir al-Barraak and he replied: Work is not an excuse for not observing an obligatory fast, such as the Ramadan fast.
Based on that, you should be patient and seek reward with Allah, for seeking reward with Him and remembering the reward will reduce the feelings of difficulty. Moreover these feelings usually arise in the first few days, then you get used to it. So seek the help of Allah, may He be exalted, and Allah will make things easy for you.
For more information, please see the answer to question no. 65803.
And Allah knows best.