Should doesn't help.
Every time you use the word "should," you're reminding yourself of what didn't happen, or presently, what is not happening.
You: "I should practice more."
Your Mind: "But I'm not."
You: "I shouldn't be upset."
Your Mind: "But I am."
You: "You should be happy you have this gig."
Other's Mind: "But I am not, and I wish you could accept how I feel."
"Should" creates false hope.
When we feel we "should" be happy, we are holding on to the hope of being happy when the present is "not" happy.
Instead, accept that you're not happy and then create paths towards happiness.
"Should" creates a false expectation.
Saying we "should" practice more, self-punishes. We silently realize to ourselves that we are not practicing and therefore, not reaching our goals. We negatively self-talk ourselves into practicing less by using "should."
Instead, accept that you're not practicing, and then create a vision of yourself improving through practice. Write out a practice goal. Then go practice.
"Should" creates a false expectation of others.
When we feel others "should" be on-time, acting a certain way, valuing what we value, we'll start to see that individual as not being like us and begin to resent them.
Instead, accept an individual is doing something different from the expectation, give them feedback in a respectfully direct manner, and ask them what they can do to meet the expectation.
At the End of It
You "should" or "should not" be doing anything - you are as you are.
Accept the present.
Resist the urge to create false hope.
Stop holding on to your expectations of other people.
Stop saying, "should."