What is the biggest challenge that you've overcome?

I've been a single parent entrepreneur for 23 of my 28 years, so I've had two generations of issues, but the one that always is the most heart wrenching is explaining to your child why you need to work at a time when your child had something else that they wanted you to do. If you can explain to them that they are your partner in this and that they will get to share in the rewards with you, the same as you are their partner in their activities and you wil support them in their endeavors, my children were wiling to accept that. In addition, if you can ask them to just give you a set amount of time, and then you will do whatever it is that they want you to do, as long as you keep your word, they will usually give you some leeway.
The other issue is that you really need to explain to your staff or your customers that when it is time for school performances etc., you won't tolerate being interupted. And you must follow through! No cell phones!