You will have to work harder, you know, if you want to succeed.

2). 副词或副词短语用作插入语,这类插入语一般放在句首或句尾。如:

Happily for him, his father's second wife was kind to him too.

You'll be able to pass the coming exam, surely.

Luckily for him, he didn't hurt in the accident.

Honestly, I don't need it at the moment.

3). 介词或介词短语作插入语,这类插入语一般放在句首,有时也可放在句中。如:

Like most of my schoolmates, I have neither brothers nor sisters-in other words, I'm an only child.

By the way, Bob sends his best wishes.

On the other hand, I didn't know you were there.

In short, things have begun to improve since schools were called on to reduce learning load.

4). 分词短语作插入语。如:

Judging from your accent, you must be from England.

Generally speaking, he is the best student in our class.

Compared with China, the USA is smaller.

5). 不定式短语作插入语。如:

To put it mildly, he was not up to the mark.

To tell you the truth, I don't want to see her.

To be sure, Jim is a faster skater, but he is not good at doing figures.

To conclude, it was a great success.