Personal God - a supernatural entity who intervenes in human affairs at the individual level.
1. Subjective evidence of religious people such as "spiritual experiences" or "hearing god" are necessarily incompatible with reality for the same reason schizophrenics are locked in mental asylums. These experiences are an extension from within ourselves and do not reflect objective reality.
2. Prayer has been tested and failed to live up to scientific scrutiny.
3. Miracles do not occur; only anecdotal evidence - a fallacious argument.
In summary, there exists no evidence to support the notion of a personal god, thus it is an irrational position to hold.