rashi explains that pas shacharis helps one overcome the allure of other women because it puts one in a state of mind that causes him to have relations with his own wife. I was under the impression that relations were only permitted in the morning for talmedey chachamim, and only if yitzro misgaber - teh gemara seems to be talking to the "hamon am"?
yonasan,
Relations are permitted in daytime in a dark house where there is no light, even for someone who is not a Talmid Chacham (Shulchan Aruch OC 240:11).
Dov Freedman