The hardest thing for any Parent I would say (and it took me a long time to get this) Is the Sacrifice of quality time with the Kids now so they can have every advantage and the best of everything later.
I burn some serious hours at work and have not had a holiday where work wasn't involved some how (even my honeymoon) But it is all worth it when I get to sit down with my daughter and watch her play violin or any Sunday where I get to watch my son play Football.
Is being successful Important to me...Not really I would be happy being poor, Is it Important to me to set a good example for my kids and give them the best possible start to life....It's worth every single second of overtime and customer complaint.