What was the toughest job you ever had?

It could be a time of employment you had, a one time side job, a role in life, or a responsibility you were given or took. What was it and what was so hard about it? Remember that what seems easy to one person can be very difficult for another.
For myself I would say being a parent is hard because so many times I'm wondering if I'm doing the right thing.
My current employment is difficult because it's so physically demanding. I'm a picker for online order fulfillment and I feel like my legs are going to fall off every day.