I agree with vampeyes that we should not generalize, i think most of loss of interest is in the mind. Some people just choice to put it way down the priority list, and lets face life can get in the way of sex. Sometimes you just want to sleep, after days filled with work, dumbass people, kids and all the stressors we face. Sometimes the mood is just not there.

Now on the other hand my theory is just the opposite. Sex to me is the greatest stress reliever. What is better after a long stressful day than a nice romp in the hay before bed time. You should always be able to fall asleep with a smile on your face.

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Love...the slowest form of suicide.