Human has self-reflecting abilities. I know excessive pursuit for morality can turn out to be a bad thing. How might we analyze this excessive pursuit of perfectionism?
You may find it useful to consider the "excessive pursuit of perfectionism" to be a form of repetition compulsion. This originates from the most basic life drive: tenacious problem solving with the aim of mastery of one's environment. (All forms of life have to manage their environments to survive.) This Life Drive (Derrida, To Speculate - On Freud) or Will to Power (Nietzsche) is very basic and unconscious, hence it can run away from conscious control. In a positive light it makes for hard-working tenacity and, for example, enjoyment of crossword puzzles. In a negative light it can get out-of-control manifesting in obsessive compulsion. The main thing to note is that the behaviour is driven by a powerful, unconscious, instinctive drive, and this is what conscious rationalization has to curb and bring under control to a reasonable level. An unconscious drive is ordinarily invisible, but by being aware of its presence and origin it can be consciously brought under control.
It would be impossible to be perfect by deciding to keep to some set of rules. As you say, you wouldn't know which rules to keep and which to break. Perfection could only come with a knowledge of what perfection means.
The reason why actions such as eating meat or killing insects matter is that they matter to the person who is acting. Whether an action is perfect or imperfect would not depend on the action but on the motives and level of knowledge of the actor.
After all, it would be impractical and unreasonable to ask people to be perfect and not inform them what this means. The practical approach would be not to attempt to be perfect by guessing what this requires, which would be hopeless, but to acquire the knowledge that brings perfection with it.
The relevant statement might be 'I and my Father are One'. It would be knowledge of this kind that allows perfection to be understood and achieved.
Meanwhile we must do the best we can given what we know and what we don't. and if we are doing this we cannot go far wrong. My view would be that the admonition to be perfect is best read as advice to be a diligent student and acquire the knowledge required to achieve this. Otherwise we'd have no clue what perfection means.
All 'in my opinion' of course.
The most famous speech given by Jesus is the "sermon on the mount", which is recorded in the Gospel of Matthew chapters 5-7. In order to provide the best authoritative insight into what perfect behavior is, Jesus analyzes boundary conditions for well-known commandments, such as "do not murder." He demonstrates that the intent to commit murder, or even a person harboring ill will toward somebody else, is contrary to the commandment.
Jesus finishes Matthew 5 by commanding, "Be perfect, as you Father in Heaven is perfect." This is an impossible standard. Because Christians have an impossible standard, they must depend on something other than their own perfection in order to be accepted.
The Apostle Paul analyzes this tension in his letter "to the Romans", chapter 7:
"But if I do the very thing I do not want to do, I agree with the Law, confessing that the Law is good." (Romans 7:16)