Expectations are born from ignorance, when we are going to do something new. It doesn´t matter if you taste new food, if you consult a therapist for the first time or if you meet a spiritual teacher. You have your ideas, your wishes and needs, and you think or hope that your expectations will be satisfied.
The only problem is that you are (completely) ignorant about these new experiences and so your expectations are something like phantasy, often far away from reality.
A wonderful and common example is when you have a problem and you go to a doctor. You expect the doctor to give you meds to get instantly cured. Today, this expectation is supported by the pharmaceutical industries and the work of doctors.
Now, if you go to a naturopath or to a spiritual healer, you have the same expectations. Then you wonder that you don´t get any pills for instant healing but that the therapist asks you about thousand things and tells you that you need to change behavior if you want to deal not only with the symptoms but also with the hidden causes. Then you might think that you are in the wrong movie and eventually you want to tell the therapist how he should do his job.
Ignorance and illusionary ideas about reality are very unhealthy and a big trap for people, especially today. The ego wants this or that but it does not ask if it is realistic. The ego is also presumptuous, arrogant and believes that it can tell experts how to handle things.
It is wise to understand these things and to be open when you do something new, without any expectations, just going with the flow.
Tasting new food might be trivial but when it is about undergoing a therapy to cope with old problems or if you want to make spiritual progress, then it is very important to be open. Ego-attitude and stupid behavior can easily kick you out. There is no law in creation which says that a therapist or spiritual master has to work with fools.
In fact, there are many nice stories where ego-focused people were sent back immediately just because they were not mature enough or ready to receive teachings or healing.
In conclusion, if you have best intentions for yourself, then be open for new experiences without delusionary expectations. And if you are a spiritual healer, therapist or special teacher, then tell your clients directly at the start that they should drop all expectations and open themselves for new experiences (like an innocent child with enthusiasm).