Don't focus on adjusting voice. Focus on getting in touch with your emotions. If you are in touch with your emotions they have an effect on your voice.

You can impress insecure girls by suppressing all emotions and simply appearing confident. That won't work with the kind of girl who is capable of being a decent life coach. Life coaching needs awareness of the emotional state of the person you are talking to. Suppressed fear that you aren't willing to openly show is very unattractive.

At the moment you listed your goals in system II matter. Connect to system one. Connect to the actual desire inside yourself on a system I level.