How is King Lear both a tragic and yet an uplifting experience?

This is the entire point of tragedy, the audience is supposed to be taken on what Aristotle calls a "growth of understanding or self knowledge" so to put the play into context, Shakespeare had to pander to the needs of the ordinary classes, most of whom were illiterate and so provide them with a moral story that was simple to comprehend. In order to do so, he chooses one of the most simple and recognisable frameworks of morality - the family. He presents the suffering of Lear at the hands of both his deceiptful daughters and as a result of his own foolishness - Lear does not recognise the love that he has in Cordelia; perhaps insecurity means that he needs flamboyant declarations of love to feel worthy - remember he is the king and so is used to having strangers declare undying love for him - so cordelia's simple declaration seems inadequit when in fact the audience knows that she is the most genuine of the three. In allowing the audience to see the folly of Lear before he recognises it himself, they despair for him and in doing so question their own morality. When Lear goes out into the storm, the feeling of despair is intensified, as the elemental clash represents feelings too intense to be articulated (even by Shakey!) The utter distress evident in Lear's speeches is enough to bring even the hardest of men to tears, as he cries to the wind and the rain to punish him, because they owe him no gratitude, unlike his daughters who have cast him out. Lear is, in effect, saying that he would rather suffer the inert punishment of the weather than the intensely personal rejection of his own children. Then there is a ray of hope when Cordelia returns, telling the audience that some love can remain even in the face of utter destruction. Lear's delight in seeing her again reflects the play's suggestion that he "loses the world and gains his soul", he is pleased to be with her and sees a prison cell as a sanctuary so long as love is there. This again is hopeful, showing how the most desperate of situations can be made beautiful with a little bit of love. The scene where LEar dies is ambiguous - it could be taken that he has convinced himself that Cordelia is alive when he is holding the feather to her mouth and, like Gloucester, "his heart burst smilingly" or it could be taken that he dies in despair, realising that his daughter is forever gone from him - it all depends on your interpretation of "look on her lips" it could be the suggestion of movement or it could be that her lips, red in life, have lost all colour and broken Lear's heart. The final line of the play is the message intended to be taken away. Edgar says "The weight of this time we must obey, speak what we feel not what we aught to say" which suggests that there is hope for the fututre, but that it lies in the hands of the living, not the laps of the dead. In this sense, the end is neutral, showing the audience that they should neither despair of or be hopeful of human nature, but rather look forward and learn. Shakespeare wants his audience to be filled with the challenge of making what will be better than what was, but does not promise that this will be the case - he makes it very clear that this will be a difficult task to fulfil but makes it sound possible. It could be argued that the end is optimistic, as the suffering has had a meaning and can be learned from, but equally it could be pessimistic because in order to gain this wisdom, so much has had to be destroyed. good luck!