When a marriage is about to be over, both spouses usually have some ability to see the writing on the wall before one of them actually says the word "divorce" or simply has papers served. But whether there is a vague sense of an upcoming breakup or not, moving on requires a certain amount of preparation in order to be able to move on successfully. The more time you are able to spend making preparations the better, because it's likely you will be able to be more subtle and be better prepared as you walk away.
Keep Your Own Money
The money in a marriage is considered either marital assets or separate assets. If the money was earned before the beginning of the marriage, or was given to you only, and not your spouse, it is separate money. That money should be kept in an account in your own name that your spouse can't access. It's a good idea to make this a policy no matter how healthy your marriage is. It is always easy enough to say you want to be able to give your own gifts to others (including your spouse) and it feels more like they are from you if they are from your own account.
Find a Financial Ally
Money that is earned during the marriage, whether it is income from a job, returns on joint investments, or business income is marital income, which you have a right to access. Some may say to withdraw half the account, but it is important to keep in mind financial obligations before deciding how much to actually withdrawal. If you can't keep a personal account secret, a friend or family member can hold onto money for you temporarily so that you will be able to set yourself up in a new place, or handle the existing expenses of your current home while you are waiting for things to be sorted out financially. Ultimately, hiding assets is against the law, so once you actually file you should be prepared to disclose whatever you withdrew.
Determine What is Important to You
Look at the different goods and services you and your spouse share. Do you have high end cable subscriptions, season tickets to the theater or a sports team, memberships in country clubs? It is likely some of these will mean more to you than others. Make a list of what you want the most, and another of things you would just assume let go of. Also, look at the assets around your home and property outside the home you own. What type of claim would you like to make? Review your lists with a family law attorney in order to get a realistic outlook on the future.
A Diplomatic Exit
When the time comes to go, or to ask your spouse to leave, it is best to keep things as civil as possible. Let them know the reasons why you want to move on without being too accusing. If you have any concerns about excessive anger or violence being a reaction, be sure you are not alone when delivering the news, and if you have children, try to be sure they are spending time somewhere else with a person you trust. It may still take time before things are looking more like you envision, but a good lawyer experienced in high asset divorce can help you stay on top of the financial end of things and give you the best chance of coming out of the marriage with your share of the assets intact.