Rather than letting go of all expectation, simply shift your expectations as required by reality, and shift them without anger or regret. If one of your predicted expectations goes wrong, use Bayes' Theorem to adjust your probability functions until your expectations are right. If expectations turn out to be unpredictable, then we might wish to not have them. I don't think that is the case.
Here's more from the Tao Te Ching:
The Master's power is like this.
He lets all things come and go
effortlessly, without desire.
He never expects results;
thus he is never disappointed.
He is never disappointed;
thus his spirit never grows old.
People focus their thoughts in the "results tank" but not in the "effort tank" or the "action tank". It's always "I want money!" not "I will learn a valuable skill and start working to use this skill." It's not that people have expectations, it's just that their expectations are often wrong and they don't adjust or take action.