Spend time in personal prayer, then write a letter of commitment and resolve to your significant other. Include why you are committing to this marriage until death, and that you have purposed to love them no matter what. Leave it in a place that your mate will find it.
What were some of the hesitations you had in writing this letter? How do you expect your partner to respond to it? How did God help you in writing it, and what did the process teach you about yourself?