This is a difficult frame of mind to adjust. Approaching your photo shoot with lack of confidence, discomfort, or just plain ole HATE for the process at hand, will 100% affect your final photographs. As we all know, how you feel impacts how you look. As adults, over time we loose confidence as our society (mostly through marketing) tells us to look a certain way. My hair is too frizzy, my legs are too chubby, my forehead-vein is too noticeable... we could all think we have a thousand things wrong with us, but guess what? You are the only one that notices. With confidence, all those little worries disappear.
Sometimes it's about warming up to the camera. Invite a friend to go on a photo adventure, and take photos of each other. Critique them and try to improve your portraits with each attempt. Working with another person would be ideal for warming up... but you could also default to taking some selfies. (The reason I wouldn't recommend selfies for warm up and/or practice is 1. the perspective is too close and 2. you need practice working with someone else looking at you through the lens.)
Are you not sure what to wear to your photo shoot? Phone a friend! Ask for their advice, and have an in-home fashion show. Or, if you need something new, go on a shopping adventure together to hunt down your new piece for the upcoming shoot.
Are you planning to do your hair or makeup different than your daily getup? Then do a trial run before photo day to make sure you really like this new or exaggerated look.
This reminds me of a statement I made in the 8th article in this series, "Prepare Your Body & Mind":
We are way too hard on ourselves just about ALL THE TIME. Watch this video for some rewire-your-brain-training:
You are AWESOME. You are INTELLIGENT. You are BRAVE. You are WONDERFUL.