A confident person doesn't say anything to himself. The question you're posing makes it seem like you're an fairly introspective person. That's a good quality, but it will not help you here.
The issue here isn't the that you're not saying the right thing to yourself. The issue is that you're approaching the problem with the wrong question.
A confident guy simply isn't introspective like that. He simply talks to people (including girls) because he likes to do it. It wouldn't make sense to him to do otherwise.
You're not alone if this doesn't come naturally to you. Remember that there are probably a lot of women out there who think the same way you do. Try to think about it in these terms, and try to find a girl who shares your point of view. Get a woman like that and the two of you will be able to share powerful thoughts and have meaningful conversations.
Alternate Scenario 1: Fake it.
In general, people are attracted to people who are similar to themselves. Mimic their interests even if it feels unnatural. Complement them about anything you can think of (not in a creepy way of course). Most will not pick up on the fact that you're a complete phony while they're being complimented--they will be too fixed on themselves.
Following this course will at least get you in the door with this person. After you're in (dated a few times) you can drop the shit and be real. By that time this person will have committed time and effort into the relationship and will have incentive to keep it going.
Alternate Scenario 2:
Change the entire frame of your mind to think and react positively toward everyone. Always assume the best intentions in everyone, and lavish everyone around you with kindness. Also be willing to help others with their problems--offer to help them move or whatever. Most of the time, all you need to do is offer to help or, listen (or whatever <insert helpful action here>). They will likely decline, but you still get the credit.
Force it! This is definitely not a natural way to behave. But being extremely optimistic in this way will make people perceive you as confident--which serves the same purpose as actually being confident. This is the mindset that I force myself into in the week leading up to a job interview. It takes a few days usually, but it will make people want to be around you.
At least one of these will work for you provided you can get over your compulsion to "be yourself." This is a purposely dramatic way of phrasing it (do I have your attention?). Here's a less severe way of saying the same thing: Seek self improvement, and adjust your behavior until you meet the expectations you have for your life.
Now go get 'em!
tldr; Find someone who is similar to you.
OR
Fake it by manipulating others.
OR
Change your mindset to think positively toward others.