在英文中，“改变以前的悲观”可以用“change one's previous pessimism”表示。
这个表达是由两个单词组成的：“change”和“previous pessimism”。
“Change”是一个动词，意思是“改变”，例如：
He changed his mind about going to the party. 他改变了去参加聚会的想法。
“Previous”是一个形容词，意思是“以前的”，例如：
The previous owner of the house painted it yellow. 这房子的前任主人把它涂成黄色。
“Pessimism”是一个名词，意思是“悲观”，例如：
He has a tendency towards pessimism and always expects the worst. 他有悲观的倾向，总是预计最坏的情况。
综上所述，“change one's previous pessimism”意思是“改变以前的悲观”。
例句：
She has worked hard to change her previous pessimism about her future prospects. 她努力改变了对未来前景的悲观看法。
He was able to change his previous pessimism about the project's success by focusing on the positive aspects. 他通过关注项目成功的积极方面，成功地改变了对项目成功的悲观看法。