Issue a public apology. This can be as funny or as serious or as creative as you want it to be.
I am sorry that I have to be the voice of reason sometimes and tell you that you really shouldn't buy the expensive toys and gadgets that you would love to have. Like Saturday, when I said it was silly to buy all three Spiderman movies (we don't even like those). Or today, when you called telling me about the computer at Best Buy. Hopefully after the wedding (and honeymoon) we will be able to indulge more and you can buy more of your fancy toys.
I am also sorry that I am sometimes not the nicest person to you. I know that my mood changes quickly and you never know what you are walking into. I am sure it was nice five years ago when we first started dating and I tried to be on my best behavior all the time. Now I am less like a lady and don't hold back my feelings around you. But, thank you for putting up with all of my moods and loving me through my crazy. I don't know how you do it, but I am sure my mother is very thankful it is you and not her.
I love you with all my heart. I am sorry for not letting you buy crazy stuff. I am sorry I sometimes act a fool.
Thank you for loving me back, always.