As a practical matter, in most divorce actions there is a presumption favoring the classification of money and assets as martial property. That means the court tends to look at whatever you have as being owned by both you and your spouse. Problems arise when there are assets one spouse owned prior to marrying, or acquired without any contribution from the other.
For example, if your parents loaned you money to buy a house that you both lived in, and you repaid the loan from non-marital funds, you may have a claim to personally retain that asset. But you still have an uphill battle under the burden of proof. You will need to show the judge a definite paper trail tracing every step of the purchase, including a copy of the loan papers, payments, bank records, letters and any other relevant documents.
Whoever claims to own the property or item must trace the whole transaction, is the general rule. Good records are essential to obtaining the best outcome. Their absence often disrupts the best arguments in defense of a position. Make a point of gathering together whatever documentation you have, and also preparing a written outline of events leading to your personal ownership of the asset. It'll then be easier to review the details with your lawyer and to develop the best strategy to retain your rights.