Translating the two meanings of 好自为之 My dictionary gives the meaning of 好自为之 as "look out for yourself". This is a positive thing you might say out of genuine concern for another person, and I think this was also the case with the original meaning for 好自为之.

However, when investigating this, I discovered that many people (mis)use it to mean something negative. Under this usage (I think), you would say it to someone whose actions you disagree with and it conveys an unwillingness to take their side or take responsibility for their (bad) decisions.

Am I understanding this right? If so, what would be an idiomatic English translation of this negative meaning?

(Note: I'm not asking which meaning is proper or correct. I'm also not asking about which meaning is more common in your personal experience, but that is also useful information.)

Here are some links in Chinese discussing 好自为之.
好自為之: look out for oneself; conduct oneself well; do one's best

There's a discussion about 好自為之
I wrote:

it is more like a warning / advice
好自為之 = &quot;better act appropriately&quot;

C Chiu wrote:

好自為之 could be used as a warning/advice. But it is definitely not rude or bad language.
From what I’ve learned, it is mostly used to encourage or inspire people to do better or make improvement. “我幫唔到你幾多﹐你好自為之啦” (There's not much I can help. You just have to do your best) is a typical way of using the idiom in a sentence, with the meaning of &quot;look out for oneself&quot;.

The term '好自為之' is  just like &quot;you better watch out&quot; or &quot;you better look out for yourself&quot; in English. It can be used as a friendly advice, but it can also be used ironically as a subtle threat.
For example:

A congressman's friend said to him: &quot;Since you went against your own party and voted 'No' on the bill, you need to watch out for yourself (要好自為之.)&quot; is clearly a genuine advice or a friendly warning.

However, if a fellow party member in the congress, who voted 'Yes', said to him: &quot;Since you went against your own party and voted 'No' on the bill, you better lookout for yourself (好自為之吧!).&quot;--  would be a subtle threat.