Couples writing their own wedding vows has become a commonplace exercise in weddings these days. It's a great way to provide an extra layer of meaning to a wedding ceremony and avoid more traditional vows that some might not agree with (i.e. that "I vow to obey you" line).
However, something I find when I witness personalized vows is that they don't actually promise anything. Often they go something like this: "From the moment I met you, I knew you were the one for me. I can't wait to spend the rest of my life with you."
Obviously I'm paraphrasing, but I usually don't hear an actual vow or promise in a couple's personalized wedding vows.
I will always remember my friend Margaret's wedding because it was the first time I had attended a wedding as a guest in a long time, but also because Margaret's vows were actual promises and beautifully written.
While she was speaking to her husband, Margaret continually used the phrases "I vow" and "I promise". THAT is what the vows you write should include.
To me, it's unnecessary to launch into the history of your relationship -- most people in attendance should already know those details. Focus on the promises and commitments that will guide your marriage and you will create beautiful vows that are both meaningful and memorable.