This popular expression is said by persons who have too much to do and who keep forgetting things they need to take with them.  Sometimes, they repeatedly forget to take the same thing with them when they go out.

我忙得昏頭轉向；要是頭不連身，恐怕早被我給遺忘了。

本句形容一個工作繁忙，忙到忘東忘西（忙昏了頭）的人；頭跟頸，若不是緊緊相連，恐怕老早忘了隨身攜帶，或者忙得「團團轉」而把它給「轉」飛了！