The vast majority of people I've coached over the years have suffered unnecessarily due to expectations and whether those expectations were "realistic" or not, is secondary, though they're usually not.
I'm afraid if you don't know how to be happy minus having your expectations met, I don't think you'll ever be happy.
Below is a simple diagram that provides access to unlimited happiness.
Invariably, there will almost always be a GAP between what you expect to happen and reality (what actually happens). Even when you say and do all the right things! Inside that GAP, you will find a surplus of frustration, disappointment, and resentment. At this point, you have one of two options:
1. Kick and scream, hoping reality will rise to meet your expectations
2. Surrender your need for control and lower expectations to meet reality where it's at
GAP (Frustration, Disappointment, Resentment)
As you've probably already guessed, reality will never conform to your expectations, which leaves you to exert more effort to create your desired reality or surrender to what is. The ego despises surrender because it sees releasing control as a threat to its survival, as a reminder of its limitations and a lesson that life does not revolve around its wishes.
"Expectations are the root of all heartache." William Shakespeare