The ego/self’s main concern is protecting the interests of the self. One of the ways it does this is by always striving to accumulate more.
More wealth, more power, more knowledge, more experiences, more friends, more skills, you name it.
And the way the ego does this (the only way it knows how to) is through personal effort - through striving and doing, working harder, working longer. And with this effort comes expectation, and when expectation is not met, unhappiness is born.
So, when we are able to let go of the self/ego, there is also a natural letting go of all these - struggle, effort, striving, seeking, and expecting, which makes way for a lot more happiness, ease, grace and flow. That is not to say that we all just sit back and do nothing with our lives. You still do what needs to be done, and that might be a whole lot of doing. However, this doing, now, simply comes without the baggage of expectation or effort.