You're right, it's very important to relax when inserting a tampon. The muscles of the pelvic floor are very strong, so if you’re not relaxed there will be resistance as you try and put the tampon in. The main things you need to do are get in the right position and don’t over think it. . Get to know your body and have a look where the tampon is going to go. Take a few deep breaths and have a go. The worst that will happen is that you will have to try again with a new tampon. Listening to your favourite music might also help you relax.