Shakespeare's sonnet 30 end with a hopeful tone when it says: "But if the while I think on thee, dear friend, All losses are restored and sorrows end." What is it referring to?

List of Past Woes

Explanation:

In sonnet 30 Shakespeare addresses the Fair Youth to narrate his past when he thinks back about his life. The poet says when he thinks how he has failed to achieve the things he wished for he has wasted so much time. In remembrance, the poet weeps for his dead friends, for the love that has long been erased. At the same time, the poet weeps over things which he does enjoy. The moment is unhappy for the poet when he recalls insults he has received in the past. The past woes are added and recorded in an accounts book though he has already lamented for those woes. It seems to the poet that he continues to pay for the past woes. But when the poet simply thinks of his friend for a while, all his losses are made and all sorrows are ended and he is happy again.