You time is such a foreign concept for busy moms. It's the reason we stay up way too late when we're already exhausted, but also so freeing that it keeps us coming back to those late nights.
Scheduling is the number one way to get your you time in. First you have to prioritize what you want this to look like for you. Is it time with friends, exercising, vegging out in front of the TV, or personal development? Figure out the top 2-3 things you'd like to set time aside for yourself to accomplish, then schedule it to make it happen. If your children are with you full time check out the daily schedules under the menu timelines to try and gain structure in your day, then use your child's sleeping times to take time for yourself.
I used my first maternity leave to go back to school and complete 50% of my MBA, all without every compromising time with my child. Nap time was go time for me, I was looking to expand my resume and personal knowledge base while at home. My MBA actually lead me to leaving my previous job to stay home with my child and work a more flexible schedule. My life took a complete shift from what I was expecting, but it happened because once I started focusing on myself and what I wanted for my family my priorities changed. I've learned from this experience that as long as you're motivated you can accomplish whatever you put your mind to! Later down the road when I finished school my priorities changed again. I then started to use my "down time" for more personal care like exercising and just time to take a break. By the end of the MBA program I was pretty run down. It's important to realize when you need a break and TAKE IT. Once you recharge, refocus your mind and reset your goals. I realize this is easier said than done, but it all starts with making your own list of what priorities you want to set for yourself and then just finding the time to make them happen.
Also don't feel bad to lean on your support systems like your spouse or family. I remember with my second child I hit a point in time where I was so perpetually tired because they were getting up every morning at 5 am. After almost a month of this and going to bed way too late because the days didn't seem long enough, my husband told me we should start splitting the morning shift. At first I didn't want to because I felt like it was more important for him to sleep and be rested for work, but I was seriously falling apart and way too overtired so I agreed. This little bit of extra sleep really helped me recharge, and the early wake ups ended up only being a temporary phase and eventually we all started sleeping again. But even this simple example had a pretty profound impact on my mood and mental health. When you have help, take it. If it's not offered, then ask for it. Remember your well-being is important too, and there's little people that depend on you to be okay, so take care of yourself too!