In the commentary to proposition IX of part 3 in Ethics, Spinoza argues that we decide if things or situations are good based on our desire for them. It is to say, the feeling we have that we want something to happen, or to belong to us, is the hint we use to label them good.
It is to say, desire comes first and is not the fruit of a conscious decision making process: we decide to reach for the cookie because we are hungry, but we did not decide to be hungry. (Or, we decide to refrain from reaching for it because mommy is watching, but we didn't decide to be afraid of mommy's anger).
According to this view, we can't choose what to want, because we make choices according to what we want in the first place.
But that does not mean we are condemned to be perpetually dissatisfied with ourselves, always unable to achieve expectations we did not choose. In the same book Spinoza also argues that when reality does not match our expectations, the problem is not with reality, which is just what it is, but with our expectations, that were not grounded in a sound knowledge of reality to begin with.
For example, a small kid could expect that if they blow hard enough in their own ship's sail, it will move forward because of the wind they created. They would be very disappointed to see it does not work. But had they opened a physics textbook they would know that the principles of action and reaction make such an idea moot from the get go, they wouldn't expect the impossible and they wouldn't be disappointed.
Here, a clarification should be made about the difference between desire or expectations and wishy washy feelings. One could argue that we could still want for something we know to be impossible, like immortality or Jedi powers. But those are two very different situations. Of course one sometimes think "wouldn't it be nice to have Jedi powers?", one can wish it was possible, but a knowledgeable person would not expect to acquire such powers, and so can't be disappointed by not having them. I might wish I had Jedi powers, but I don't act in order to get them or feel like acting towards this goal, I don't desire Jedi powers. It would make about as such sense as to be disappointed that I can't grab the moon by reaching with my hand because it looks so tiny from Earth.
The point I am getting at is, the more we know ourselves, the more our expectations about ourselves tend to match reality and be achievable. This does not mean we have to give up all expectations. We shall always strive for realistic betterment, but knowledge helps us strive for what we can actually obtain.
Instead of feeling bad for not realizing unrealistic expectations, learn about our mistakes, analyse what fact we didn't consider that made our expectations unrealistic, and work toward a better, more suitable goal. Educating ourselves won't help us decide what to desire, but will inform our desires and have them match reality. While this is a way we can influence what we want, note that it is still not a choice as we can't choose what reality is made of and will bring forth.