Here’s why:
You need to do unique things for yourself to give your spouse someone interesting to love.
You also need to do unique things for yourself for your own happiness.
For your spouse
Think back to when you were dating for a minute. When you were dating, you would find new and interesting people. These people had different friends than you, went to different restaurants, liked different music, etc. Even if you didn’t end up marrying them, it was still fun while it lasted. Just them being unique made them interesting and exciting.
The same goes for you. If you’re not being unique, you’re becoming uninteresting to your spouse. Keep up with hobbies you like. Maintain those old interests that got lost along the way.
Yes, you have children right now, and they take up a lot of your priority, but if you lose yourself too much, you’re going to lose your marriage, too.