Marriage is something like a basket. A strong, sturdy basket and in it a woman puts everything; finances, kids, her sensitive heart and tender soul as well. You are the hot air balloon at the top of that basket and together you should expect to soar to great heights and women feel safe. Some have never in their lives felt truly safe before.
Sometimes there are distractions and although some are good, as they mount and multiply, a woman's sense of security begins to fade. This upsets her deep inside and she might not know how to handle that.
What is harder is when the basket is turned upside down on her. It lashes out at her for being scared and trying to keep her balloon on track. A dark sadness may come over her and she might not be able to stop it for she knows she can not make her balloon go where it does not want to go but without it, she goes nowhere.
If you want to understand your wife and don't, remember that it is you she looks to for strength and stability. It is you she wants to turn to to share her deepest fears and darkest secrets. She is a different being and always will be. It may not always be clear to you the what and why but if you stay focused on the woman you love and not how her feelings affect her then you can navigate together and go wherever you choose.