How could you say "NO" without hurting others? Well, try the following sentences.
I can't right now, but maybe later.
这意味着将来可能行。
Unfortunately, I've had a few things come up.
这是指有意外的事情发生了。
I'm trying to focus on finishing off some other things.
这是另一种方式表示你有一些没有完成的工作。
I'm sorry I can't.
这直接表明了这对你而言是不可能的。