Let's think this thing through just for a moment. The only (physical) difference between masturbation and sexual intercourse is what is providing the "pumping action" to the penis to prompt the orgasm. Hence, should masturbation cause one to lose his memory then there are many married couples who can remember nothing. Actually, this is one of the many myths concerning masturbation that was most likely put forth by concerned parents, etc who wanted to discourage this activity. The only real way it would affect your marital life I would think would be if you used excessive pressure which may make it a little more difficult, over time, to get adequate stimulation from your mate. The primary question concerning masturbation really has to do with your upbringing and whether it is counter to your religious views or not. However, unless you use too much pressure, there should be no medical reason to avoid this activity.

Wrong. For example, prolactin level is 400% higher after sexual intercourse compared to level after masturbation. But that is not the problem s.intercourse vs masturbation.
Orgasm activates hormones/neurotransmitters and hormones/neurotransmiters temporarily change cognitive functions.