writting your own vows

So when my FH and I went to the church, we were asked the ? of 'Do we plan on witting our own vows'? Before I could say anything my FH says 'yes of course we are witting our own vows'. I was shocked, and now I am just freaking out. Did anyone or does anyone plan to write their own vows, did your try to make them sound traditional like an
I promise
or an
I vow to

I am totally lost over this. Should they just be short and simple or very detailed. I haven't been to a wedding were the couple wrote their own vows.