I shared this in another post, but will repost here.
To grow into a salesmen skin is very helpful for startup founders (and doesn't come natural to many), which I think comes down to ability to ask for things often and building tolerance for hearing no. To overcome the hesitation to ask and "ease into it" in your everyday life start asking people for things - better table at a restaurant, room upgrade at a hotel, discount for your purchase at a store checkout. You will be surprised how often you will get things for asking and it will be very encouraging, while hearing no doesn't set you back in any way. When you run your business you will be asking many people for many things - help you spread the word, sign up, upgrade, etc. so turning asking into a natural habit is my favorite life hack.