1. Ignore everyone's "helpful advice" or "scolding". You can ignore my advice here if you wish.
2. You have experienced a loss of something with emotional attachment. It is ok that it hurts for the time being. It is normal. don't let anyone to tell you to "just get over it". Or "it's just stuff."
3. You will go through a grieving process. This means that, over time, you will get over your loss. You will build new positive memories that overlay the old. You will appreciate what you still do have - your family, your friends, your memories of good times. It won't happen instantly, but it will happen. So give yourself the gift of patience with yourself, forgiveness, even the permission to eventually "let it go". Remember, 95% of the rest of your cruise was amazing, I"ll bet. one day, but not right away, when you look at photos, you'll remember how happy you were in the pictures, what you were doing, the fun you've had, and notice less and less the jewelry you were wearing.
4. One final note -- your willingness to share your story with others is a gift you have given. You have already probably helped someone avoid making a similar mistake in the future. Your loss will help somebody else in the future not have to go through the same thing. It doesn't bring your items back to you, but it is an act of selflessness for others. You might not ever know their gratitude, but I'll bet everyone who reads this post is thinking "I am really, really, really going to make sure that I triple check our safe before we leave our cruise". And at least one person will find something they nearly left behind, and they will have you to thank for it.