I'm about to go now.

到别人家拜访，到达的时间很重要，最好是先预约(make an appointment)，离开的时间也是大学问。例如你到人家拜访，下午茶也喝完，主人家开始准备晚饭，你仍然未离开，通常主人家会礼貌地叫你留下来吃晚饭，不管你真的想留下还是借故离开，也该客气地回答：I'm about to go now.（我即将离开）或I'm just about to leave。About、Just about是‘差不多’、‘快将’的意思，例如：I'm just about twenty.就是‘我差不多20岁’。
对话
Ａ：I'm about to go now. Yeah, I really like this place. I don't want to leave. It's really comfortable and nice and this couch, do you mind if I sit down on again? ...
Ｂ：When will you be leaving?
Ａ：Well, I'm about to go now.
Ｂ：Look at the clock, you said that two hours ago.
Ａ：Clock? Yes, it is an interesting clock...
甲：我差不多走了。我真的很喜欢这里，不想离去。这里真的很舒服，这沙发很舒服，可否再次坐下？............
乙：你何时离开?
甲：好啦，我快要走了。
乙：看看钟吧，你两个钟头前已经这么说。
甲：钟？对呀，很可爱的钟．．．

I'm about to go now（我要告辞了）的about to是‘即将’、‘正打算’的意思。要强调，可加just一字，例如：We must hurry. The train is (just) about to leave.（快点，火车要开出了）。留意not about to往往不是说‘不会很快’，而是‘不愿意’的意思，例如：I'm not about to do your work for you（我不会为你代劳）。

有些客人说话喋喋不休，才说I'm about to go now.，又絮絮叨叨说这说那，这英文称为long-winded，直译是‘气息长的’。听演讲，一般人最怕的是a long-winded speaker（喋喋不休的讲者）或a long-winded speech.（长篇大论的讲词）。

总之，到亲友家里做客，切勿逗留太久，否则徒讨人厌。英文成语to outstay / overstay one's welcome直译是‘逗留超过了欢迎期’，那是说逗留长得不受欢迎了，例如：Although they asked me to stay "a few more days", I decided to take leave, not wanting to overstay my welcome.（虽然他们邀我‘多住几天’，我还是决定告辞，恐怕逗留太久，徒讨人厌）。

英文谚语说：A guest and a fish after three days are poison.（鱼过三天不新鲜，客过三天讨人厌），又说：The first day a guest, the third a pest.（第一天是客人，第三天只恼人）。现代人生活繁忙，客人逗留不要说三天，就是三小时，恐怕已经成为poison（毒药）或pest（害虫、讨厌的人）了。