Nice, all good advice and still relevant for some of us adults with a few words changed...
I don't have a problem with the advice "life isn't fair, get used to it" because I think reading it as a justification for people stepping over one another is a very narrow interpretation. There's many times life just doesn't feel "fair" such as falling in love with someone who just doesn't love you back, training for a marathon and after months of training and two weeks before the race you pull a hamstring muscle, throwing your hat in for a promotion and your co-worker gets promoted instead.
Anyhow, just my thoughts.