Explain to her why she should be happy about your masturbatory practices.
Just tell her how you turn them inside out. That way you get the lubrication and none of the mess!
In the long run she will thank you for not having all of those pesky, flying cumshot stains like the ones I have on my clock radio, wall, and ceiling ( I was pretty turned on when she jumped off my shitand BAM!)
If that doesn't work- just start jerking into tissues...
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quack quack