Fainting in the mind is rooted in exhausted emotions,  emotional  exhaustion is a chronic state  of physical and emotional depletion that result from excessive job and/ or personal demands  and continuous  stress. It describes a feeling of being emotionally overextended and exhausted by ones work. Highly sensitive big hearted people are more predispose to experience this condition. Bighearted people often take on too many tasks, spreading themselves to thin,  not allowing the spirit time to restore, It is in their nature  to worry about the needs of others putting their own wants and needs on the back  burner. Overwhelmed by problems, and mounting pressures, they lose focus fainting in our minds brings a loss of spiritual consciousness, and with this the inclination to charge God foolishly. We are to work steadily, but realistically, and expect to reap "in due season" we are to serve while being "meek and lowly" avoiding the wearying burdens of self pity and hypocrisy. We are to pray always so that we will not faint, so that our performance will actually be for the welfare of our souls, which is so much more than just going through the motions.