Scarlett Johansson may be one of the most lucrative movie stars of all time , but that doesn't mean that motherhood's a breeze for her. The actress opened up about the challenges of being a working mom to ET at the American Foundation for AIDS Research's New York gala this week. Johansson said that raising her 2-year-old daughter Rose and filming blockbuster movies is tricky, as it is with many other mothers in the workforce. "I don't profess to know anything about parenting, anything more than anybody else, [but] being a working mom is an incredible challenge, [and] it's an incredible gift," said the actress, who reportedly split from her husband of two years Romain Dauriac last month. "I think you always feel a little bit of guilt… If you're at work, you feel like you're missing out on those special moments with your kid. If you're with your kid, you feel like you're not giving enough to your job. It's a balance." The Ghost in the Shell star added, "I have a lot of huge admiration for working moms...I'm barely, barely holding it together." If a woman with all the resources in the world is having difficulty keeping it together, that says volumes about the stresses facing less advantaged working mothers.