In the first part, I showed how boredom in relationships came from feelings of insecurity, not feelings of safety.
The same applies to picking up chicas as a single guy. The more secure you are in who you are, the more risks you will take. The more risks you take (such as making your sexual desires known), the more likely you are to get laid.
Likewise, the more insecure your are about yourself, the less chances you take. Any tiny hint of rejection or failure would crush your ego and self esteem, so to keep the status quo (no sex, but no rejection either), you refuse to take a risk and put yourself out there.
To summarize - the more confident you are, the more likely you are to risk rejection, the more likely you get laid (or whatever else it is you go after). The less confident you are, the less like you are to risk rejection, and the less likely you are to get a girl (or whatever else it is you go after).
Quit doubting whether you are good enough for something, go after it and let it reject you.