"In him we live and move and have our being’; as even some of your own poets have said, “‘For we are indeed his offspring." -Acts 17:28 (ESV)
What is the justification for our existence? (What is the purpose of life?). To be fair, the "reason" would have to qualify for all human beings on the planet. Some people think its their career- which could be understandable for the doctors and teachers and politicians who are socially seen as making a difference. What about the street cleaners or janitors at your local high school? Or the unemployed? Or the special needs and disabled who aren't able to work. a job? We can't base our existence on that one. We also can't base it on our "title" such as mother, father, caretaker... etc. Not everyone can be or wants to be a mother or a father.
Why do you exist? Because God created you -specifically you- so that you can enjoy Him and He can enjoy you. You exist because He wants you to. Sure, being a mother is wonderful! Being a doctor or a teacher or even a hairstylist are great things to be! But that's not why you're here. There have been plenty of those things before you and there will be plenty after but why YOU and I exist- it's for God alone. You wouldn't be alive if He didn't want you here.
Once you realize this nugget of truth, it will put your whole life into a clear and stress free perspective. Your identity and value lies in the truth that God is your creator and He loves you enough to think the world needed one of you! THAT should make you giddy with joy and fill your heart with praise and adoration for our Creator!