I should have worded that differently. I was being a dork and using "the good stuff" as a euphemism for having sex, which is what I assumed you were talking about when you said he had extra girlfriends on the side. It hurts the man if a woman holds him to no standards because if things come too easily for him his entire life, he learns to accept a lesser version of himself and then acts out when a woman holds him to a higher standard. This means he will treat women with standards badly, and end up with a women with very low standards who will accept his behavior or just constantly nag about it while staying and accepting it. Then he can convince himself that any woman is just a nag who doesn't "accept" him. This creates a dislike and mistrust of women and no woman (the ones with high standards OR low standards) are ever "good enough" for him. This makes it more acceptable to continue the self-defeating behavior.
This is similar to super good looking people getting by on their looks while failing to develop as people. A lot of people who exhibit the above described behavior probably fall into this category as well.
And what you said about the woman and attachment... biologically women usually become attached through sexual intercourse. There are attachment factors for both men and women, but it is much stronger in women. Here is some info on research in 2006 that confirms the attachment and explores a few additional theories.
Here's a bit from this study: http://www.encyclopedia.com/doc/1G1-156736546.html
Negative emotions that signal incompatibility with relationship goals
"When one's sexual goals and desires are violated by a partner, distress and other negative emotions are generated (Buss, 1989a). This follows from the definition of emotion as a signal about environmental events that have consequences for personal well-being (e.g., Mandler, 1975, 1984). Because men and women had to cope with different adaptive problems in both short- term and long-term mating strategies (Buss & Schmitt, 1993), different events would activate negative emotions for men and women (Buss, 1989a). For example, women have evolved a more emotional-interpersonal orientation toward sex, associating sex with expressions of love and affection (e.g., DeLamater, 1987; Gagnon & Simon, 1973). Accordingly, women are more likely than men to expect partners to be responsive to their emotional needs during heterosexual intercourse. When these relational expectations are not fulfilled, reproductive success may be threatened and negative emotions such as disappointment, anger, and resentment, as well as preoccupation with relational concerns, may result. Behaviorally, these affects may be reflected in indifference and emotional detachment from the sexual event and partner (Birnbaum & Laser-Brandt, 2002). "
About being thankful...
just ask yourself what you learned and be thankful for that.