1.keep on doing继续做事
继续做某事（有时可能含有间断地继续做某事，但是更强调“反复”和“决心”，而且附加感情色彩。）
I keep doing my homework.我一直都在做作业。 (强调持续性)
I keep on doing my homework even though it's boring.
即使作业很无聊，我还是要坚持做。 (强调坚持不懈)
I've got to keep doing this kind of thing.
我必须继续做这种事。 (强调持续性)
The important thing is to know what to do and then just keep doing it.
重要的是要知道该做什么，然后坚持下去。 (强调坚持性，有决心，反复去继续做)
Never keep on exercising if you have even the slightest chest pain
即使你只感到很轻微的胸部疼痛，也不要继续锻炼。（强调锻炼时有间断性的继续，不可能是持续不断地那种继续）
The ceasefire itself could prove stillborn if rebel units in the bush keep on fighting.
如果丛林地带的叛军继续开火，那停火协议本身就可能起不到任何作用。（强调显然继续开火中间有一定的间断）
Don't keep on bothering me.
别老磨人！（带有感情色彩的）
2. keep someone on就是在某人要退休或失业的时候，继续留用或雇用某人
If you keep someone on, you continue to employ them, for example after they are old enough to retire or after other employees have lost their jobs.
Sometimes they keep you on a bit longer if there's no one quite ready to step into your shoes...
有时如果没有顶替你的合适人选，他们会继续雇用你一段时间。
3. keep sb. on one's toes 使某人保持警觉：确保某人全神贯注于自己所做的事情，并为可能发生的任何事情做好准备
直译为“用脚尖站立”,比喻随时候命,召之即来，来之能战，战之能胜的状态,或者说很有精神、脑子一直在转的状态.而Keep my juices flowing也有同样意思。保持警惕、专注、活跃，一种备战的状态。
请看例句：
They should keep them on their toes until their enemies are vanquished.
他们应该一直保持警觉性，直到他们的敌人被消灭。
His fiery campaign rhetoric has kept opposition parties on their toes for months.
他激烈的竞选言辞使反对党派一连几个月都保持警觉。
The boss made regular inspections in order to keep employees on their toes.
老板定期检查，让员工时刻保持警惕。
Surprise visits help to keep the staff on their toes.
突击巡察有助于使员工常备不懈。
Thanks for keeping me on my toes.
多谢提醒！
Until then,I say we keep them on their toes.
但在那之前，我们还是给她们点警告。
Having two wild and active daughters keeps me on my toes.
有两个疯狂好动的女儿迫使我必须保持警惕状态。
Nobody likes uncertainty, but it does keep you on your toes.
没有人喜欢不确定的事，但它的确会使你保持警觉。
4.keep on about/at 喋喋不休，对……纠缠不清
Mom always kept on me about my homework, and I'm very grateful to her for that.
母亲以前经常喋喋不休要我做好功课，对此我非常感激她。
She kept on at him to get some qualifications.
她不停跟他说，让他去考取一些资格证书。
He kept on at me to such an extent that occasionally I wished he would get off my back.
他一直对我唠叨个没完，有时我真希望他不要再烦我了。
He used to keep on at me about the need to win
他以前总是跟我唠叨必须获胜才行。
You've constantly got to keep on at people about that
你总是得没完没了地和别人说那件事。
I'll do it ─ just don't keep on at me about it!
我会做的——可别再对我唠叨了！
If he doesn't agree, just keep on at him until he does.
他不答应，你就跟他磨。
He kept on about me being 'defensive'.
他唠叨个不停，说我“有戒心”。
Stop keeping on about it!
别再唠叨那件事了！