All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
Leaving a job and being ambitious to have a better one because of insufficient income is not considered discontent with the Fate of Allaah The Almighty. Discontent is to react to Fate with outrage and objection; which is not the case when one looks for a more lucrative job. It is important for you to know that it is impermissible to leave your job even if it generates a low income, until you find another one so that you do not have to seek financial help from people.
Your wish to improve your condition is not considered discontent with the predestination of Allaah. However, yearning to improve ones financial status is not the best state for the believer, as the Prophet, sallallaahu ‘alayhi wa sallam, urged Abu Hurayrah to be. Perhaps your mother’s intention was to guide you to adopt this state, for it is undoubtedly the best and the most perfect one.
Allaah Knows best.