I don't think you can 'fool' your senses in that sense, if you pardon the pun - stimulation of the nerves and synapses that give sexual pleasure react in a similar, though slightly different way depending if the stimulation is applied by 'flying solo' or not. The male ejaculation is a programmed response to certain stimulation, regardless of wether or not a vagina and uterus will be receiving the sperm as nature intended. It is a perfectly natrual function - it releases tensions within the body, and it teaches bodily responses, and how to control them, which can play a vital part in avoiding premature ejaculation. Apart from anything else, it's one of the few activities where you really can 'please yourself', and it's free!