Your Expectations are Valid

'NO EXPECTATIONS, NO DISAPPOINTMENTS.'
If the message in the quote above is telling me not to have expectations from people so that I don't get disappointed, it is heavily flawed...Expectations and disappointments are inevitable.

I bet we all have expectations in various dimensions of our lives, including the author of this quote in question. It is abnormal not to.
Expectations provide a yardstick to measure the quality and performance of relationships; whether it's a business/work relationship where expectations are explicitly stated and tasks are executed to meet specified deadlines, or in intimate relationships where expectations are more implicit and affection, companionship and emotional support are mutual needs.

All healthy human relationships thrive on reciprocity; if it is one-sided, it loses balance and crashes.
People do not have to do for you exactly what you do for them but if they don't make an effort to match your gestures, you might be better off without them.
Pouring yourself into someone that does not give any back will leave you physically drained and emotionally bankrupt.
If you don't know your worth, people will present you a shabby bargain.

That somebody can not meet your expectations does not invalidate them, when you treat people right, you have the right to expect same back.

Ciao.