One of the many uses of 就 (jiù) is to add emphasis to indifference. This is similar to when we say in English "if you want to do it, then just do it!" and swapping out the "do" in that sentence for some other verb.
Structure with Verbs
This structure will usually add emphasis to what are saying, and it often expresses that the speaker has an "I don't care" attitude.
Examples
- 不吃就不吃，你以为我很想吃啊？ Just don't eat, then. You thought I wanted to eat?
- 去就去，反正在家也没事。 If you want to go, just go. There's nothing happening at home anyway.
Structure with Negative Adj.
Negative Adj. + 就 + Negative Adj.
You can also add in an adjective with a negative connotation. The use is the same here.
Examples
- 不满意就不满意，我也没办法。 Be dissatisfied if you want, but there's nothing I can do.
- 她不高兴就不高兴，又不是我的错。 If she's unhappy, she's unhappy. It's not like it's my fault.
- 生气就生气，谁怕谁！ Get angry if you want. You think you scare me?
See also
Sources and further reading