For me even as a guy, despite what people see as a cool, laid back exterior, I know that i'm an emotional wreck a lot of the time on the inside. A few things that I think help to solve those problems. The first one is trust. I know I wouldn't trust a person overnight or anything but once the relationship gets to a serious stage, trust is very important. Once you let go and trust the person, that takes care of being clingy. Trust not only helps you to relax about the person's whereabouts or who they hang out with or things of that nature, but it also gives you an at ease mind to know that they love you and are coming home to you at the end of the day. Of course with trust there always comes risk, but the greater risk is to let fear overcome you and eventually maybe even become the reason for your relationship to end. Insecurity, I think we all have that problem to an extent. But hopefully your partner will be someone who re-assures you of why he loves you and wants to be with you. As for what you can do for yourself, try to think about all of the positive qualities you bring to the table.. Don't let your mind get filled with doubt or negativity. Impatient and crazy... Again, I'm one of the most impatient people out there as well, especially in a relationship. I don't like not knowing whats coming next, and my mind goes at a million miles an hour to try and figure it out rather than living for the moment and letting it happen naturally. I think that even in a relationship you need to make sure to have your own life. Try to do things outside of work or whatever it is you do, try to do some extracurricular activities to occupy your time. The less free time you have the less time you have to worry about your partner, or whats gonna happen next with your relationship. For the overthinkers, give your mind something constructive to work on. I don't really know how well I answered your question but hopefully it helps a little.
Be careful with your heart, because when someone seems too good to be true, they usually are.