I am inclined to think him pessimistic, but mainly on hearsay. I have not read World as Will and Idea in total, but I have read passages and numerous glosses of it and familiar with the main ideas. I will add that I think he was a very brilliant mind and substantially correct in most of the important respects. But I think he was personally a somewhat tempestuous and overly emotional individual, which coloured his philosophical outlook. I agree with Schopenhauer in respect of the idea that existence itself is problematic, but the way in which this is to be understood is a very delicate matter. It is very easy to turn it into simple pessimism. It is interesting to note that in Buddhism, which was a great influence on Schopenhaur, the desire for the cessation of existence is as much a hindrance as the desire for its continuance.

Yes, even Schopenhauer himself admitted in numerous of his passages that his philosophy is pessimistic. But one has to put into account that that does not mean it is not true.
I especially recommend his essay On the sufferings of the world, where explicitly demonstrates why is the way of life and existence of the world pessimistic and goes even so far of admitting that non-existence would be preferable for mankind if only it could apprehend the world with the objective eye.
However, despite that sombre look he did provide two ways of escaping that suffering of the world - through practising art and compassion one can escape but just temporarily, indefinitely there is only one way and that is the annihilation of the will itself through the intellect; e.g. ascetic life of saints and buddhists.

On the other side, regarding his numerous well grounded attacks on Hegel, Fichte and Schelling, I can say that he did not tolerate fools well and especially not charlatans who practised philosophy as a means for their progress in society and not for philosphy itself. His only standard in philosophy was following the truth and nothing more. I can agree even in his remark about Hegelian philosophy where he said that when reading this sheer nonsense like his Phenomenology of spirit one can imagine himself being in a madhouse. According to all confusing concepts without grounded substance found in that work I think Schopenhauer proved right.

Anyway the whole of his philosophy is derived from the all pervasive will which can be found in all inorganic and organic nature ans is the sole cause for all sufferings in the world. People are constantly found somewehere between pain and boredom.

I agree with the above comment that he is one of the most complete philospher ever lived, because if one read his masterpiece The World as Will and Representation he will find unparalleled prose in style of beauty, elegance and intelligence.

In his explanation of the world I think he came as close as human mind can get. Imo - True genius.

If you want a safe compass to guide you through life, and to banish all doubt as to the right way of looking at it, you cannot do better than accustom yourself to regard this world as a penitentiary, a sort of a penal colony, or [Greek: ergastaerion] as the earliest philosopher called it.[1]
Amongst the Christian Fathers, Origen, with praiseworthy courage, took this view,[2] which is further justified by certain objective theories of life.
I refer, not to my own philosophy alone, but to the wisdom of all ages, as expressed in Brahmanism and Buddhism, and in the sayings of Greek philosophers like Empedocles and Pythagoras; as also by Cicero, in his remark that the wise men of old used to teach that we come into this world to pay the penalty of crime committed in another state of existence-a doctrine which formed part of the initiation into the mysteries.[3]
And Vanini-whom his contemporaries burned, finding that an easier task than to confute him-puts the same thing in a very forcible way. Man, he says, is so full of every kind of misery that, were it not repugnant to the
Christian religion, I should venture to affirm that if evil spirits exist at all, they have posed into human form and are now atoning for their crimes.[4] And true Christianity-using the word in its right sense-also regards our existence as the consequence of sin and error.

If you accustom yourself to this view of life you will regulate your expectations accordingly, ..
[unquote]


Other than the core principle, I believe we should not take the above examples given too literally but filter out what is not practical and ineffective to one's circumstances.

Well I can't disagree with any of that, I think it is completely true. There are also strong echoes of stoicism in this outlook.

Stoicism as an attempt to use the great prerogative of man, reason, for an important and salutary end; to raise him above the suffering and pain to which all life is exposed, is valuable, but it relies too much on reason itself, is basically too rigid and idealistic.
The rigidity culminated in a contradiction, i.e. by reason, suicide should be recommended (like a medicine) to end any incurable suffering, but this is not recommended, why cannot, there is no proper answers to that.