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.
The other concept indicated in the last paragraph on "results tank" not "effort tank" is lust of result. There aren't as many sources discussing this topic directly, but Zen in the Art of Archery  is good, as is Watts' Way of Zen .
I highly recommend them all for anyone interested in creating things.