我明天有事情要做。
【英文对比翻译】
Chinese Style —— I have something to do tomorrow.
American Style —— I am tied up/busy all day tomorrow.
【点评】
用I have something to do来表示你很忙，这是比较中国式的说法。虽然有时我也能听到老外说。比如有人要你帮忙做某事，可以说I am so sorry that I have something else to do now.因为每时每刻我们都有事情要做，躺在那里睡大觉也是事情。所以你可以说我很忙，脱不开身：I am tied up.还有其他的说法: I can't make it at that time. I'd love to, but I can't, I have to stay at home.
所以我个人认为这样拒绝别人会比较委婉礼貌，而不是说I have something to do显得态度强硬，不耐烦。