如果你想要挑战，你可以用英语说"I want to challenge"或"I'm up for a challenge." 例如：
"I want to challenge myself to run a marathon next year."
"I'm up for a challenge and I'm going to try to learn a new language."
这两个短语都表示你有兴趣接受挑战。"I want to challenge"指你主动寻找挑战，而"I'm up for a challenge"则指你已经准备好接受挑战了。