Historically speaking, the usual way to reach aromanticism for males was castration. Less, um, decisive methods included fasting (starving, really), LOTS of praying (getting into an alternate state of consciousness, really), and physically removing oneself from the sources of temptation (poor sheep).

Here's how St.Benedict dealt with it, for example:

Suddenly, the saint’s mind was filled with the memory of a “certain woman … which some time he had seen.” The mere memory of her “mightily inflame[d]” him with desire for her. Then, just as soon as he had been nearly overcome with passion, God intervened. Here is how Pope Gregory describes it:

But, suddenly assisted with God’s grace, he came to himself; and seeing many thick briers and nettle bushes to grow hard by, off he cast his apparel, and threw himself into the midst of them, and there wallowed so long that, when he rose up, all his flesh was pitifully torn: and so by the wounds of his body, he cured the wounds of his soul, in that he turned pleasure into pain, and by the outward burning of extreme smart, quenched that fire which, being nourished before with the fuel of carnal cogitations, did inwardly burn in his soul: and by this means he overcame the sin, because he made a change of the fire.

You want to subvert some of your basic, biologically hardwired drives. If you manage to find effective tools, I suggest that the chance to seriously fuck yourself up is high.