If you don't know your objectif, don't keep two cards of the same color which could be your objective. If your target is that color, it's possible your teammates wanted to react to your play for any reason, and if you keep them until the end, you force the plan to change, and since you are the person with the least amount of information, that usually lead to your objective with a high chance to not be done.

When you have more than one way to do all objectives, choose the one where the co² cards of the next age will be present at the end of the age.