Here some sentences close to it, in sense:
Don´t expect too much of people, the less you expect the less you will be disappointed.
Too much expectation leads to sadness.
If you expect too much from others it can hurt you in the end.
Too much expectation hurts in the end.
Of course, there is the other thought, that when one expects too much of others, he/she is giving too much leeway to others influence in his life and life style. And that a grown up has to chase after his own dreams...and work hard for them.