A while ago I read a beautiful post about the "Why" that's underlying of a red pill principle. I was fascinated by how many people enjoyed to see the "Why does this principle work?".
It is essential to understand that all behavior is conditional, including love. Everything is based upon conditionality. Your friends like you, because of the fun you provide when you're with each other, or because of the emotional support you provide. Friendship is conditional. Remove the fun and emotional support, and the conditionality of your friendship will show.
Love is also conditional, just like friendships or work relationships. People, men and women, are looking for things the other sex can provide whether that's sex, comfort, a nice ass, a sixpack, a stable financial situation, gifts, hugs, you name it. You are in exchange of goods. When both parties are happy with the deal, a happy relationship forms (Whether that's an LTR, FwB, plate relationship).
Now here's the fun part: You're in near constant negotiation within a relationship. You're both playing with the goods that you're offering. A women will withhold sex if she's a good negotiator. A man will withhold comfort if he's a good negotiator. There are other goods for negotiation, but comfort and sex are the two biggest. What's important to understand is the following: The fact that she's negotiating means she's interested. Nobody is negotiating for something that they don't want.
Abundance mentality ties in with the following: The person that can walk away from the negotiation the easiest has the most power.
The person with the best alternatives has the easier time walking away from a negotiation. An employer with three other candidates beside you had the most power. An employee who knows the company needs him for the operation has the most power.
Abundance means other options, and with other options comes the mentality to being able to walk away from the negotiation. This in turn gives you the power in a negotiation which results in an increase in the goods from her side (sex, love, affection, flirting).