Which is worse of these 2 terrible reasons for believing something? A: "It makes me feel good." B: "It's what my family all believe."
David Hume said "A wise man proportions his belief to the evidence", and certainly on the face of it believing something without evidence just because it makes you feel good is irrational.
However, life is hard. Imagine a severely depressed man who is suicidal, who has found no relief through counselling or medicine - it would be perfectly rational for him to want to alleviate his suffering, would it not? And if he 'found God', and that gave his life meaning and purpose and consolation (albeit false consolation), lifting him out of his depression and literally 'saving' him - i.e. if believing in God alleviated his suffering, would that not be perfectly rational?
Believing in something just because it makes you feel good is irrational, but wanting to feed good is rational. A man can believe the most ridiculous things - that Joseph Smith found golden plates inscribed by God buried in a hill, for instance, or that an alien overlord Xenu threw human souls into volcanoes - but if believing ridiculous things makes your life worth living (and as an atheist and materialist myself, and a firm believer that this life is all we're going to get) well, you gotta try and live happy, right?