I'm not claiming to be a mystic or even to have a clear idea of what a mystic is, but it seems to me that to the extent that the statement in the OP is true, it is so because
1) As once taught to me in a LamRim Buddhist group, there is no good fruit to be had from the decisions of an afflicted mind. Therefore, while it is certainly necessary to pursue truth, it is not the utmost priority. A person must ensure a certain degree of peace and harmony first, even if it compromises the extent to which he can understand truth.
I don't want to make it appear that I am agreeing with those who think "feeling well" is all that matters. I actually despise that mindset. But there is much practical wisdom in recognizing that people need a modicum of harmony and happiness, and that one's mental faculties are vulnerable.
2) That said, and as Alceste pointed out already, there is a kind of calm acceptance when one is aware of how much there is wrong in the world. The expectation of a world that is "all right" is, after all, very much a delusion, and it is possible to draw a lot of mental and spiritual fortitude from the refusal of feeding that delusion. Even more important, letting go of that delusion makes one's goals both more convincing, more meaningful and easier to choose, so in that sense it is far more engaging and motivating than anything that could be had with that delusion. Such a solid faith can be very reassuring indeed, despite superficial appearances to the contrary.