I congratulate you for your decision and I really do believe you are on the right track, but may I make a suggestion? I think that deciding that "today is the day you will change your thinking" is the exact type of thinking that creates your stressful patterns. You feel like you must change who you are and how you deal with life in order to "deserve" your success and positive relationships. I think before you will really start to feel you are making any progress you need to relax and enjoy yourself and not put pressure on yourself to be someone you are not. You naturally care a great deal about they way you live your life and you want to do things the best you can. These are not negative traits - they just create stress and stress does detract from our enjoyment of life. What you need to start changing is your outlook on life, not who you are. You need to learn to relax, prioritize things properly (fun is a lot higher on the list than most people realize!) and most of all don't beat yourself up for not being the "carefree" person you have decided you want to be. If your partner sees that you are really trying to learn to deal with your stress if he really loves you he will support you and also have the patience to wait for you to figure it out in your own time. I think you are already well on your way. In addition to meditation I found yoga has been a huge benefit in helping me deal with my anxiety and stress issues - plus it's more active, which helped a me a lot as I am a twitchy person and meditating was HARD at first.
Anyway, best of luck and remember that the most important thing is to be patient and loving to yourself. You've already taken many important steps and I know that you are well on your way to living the life of your dreams.