Writing critique request: the almost imperceptible effects of Zhou Ziwang's injection
Other than little wordy, and sometimes choosing less effective words, there's no major mistake in this piece. 

Suggestions:


其实当时那支注射器有意外甚至不易察觉的影响 (ambiguous word: 意外 can also means "accidental". If you meant 'surprising' or "unexpected", it should be "意料之外" or "意想不到" ) --> 其实当时那支注射器(对我)有意想不到，甚至不易察觉的影响 ( add '对我' to identify the object that's being effected is 'me', or else we don't know if it is effecting the world or the future) 
在做日常活动的过程中 (wordy) -->在日常活动的時候 
我的行为几乎感觉不到任何变化 (wordy)-->我的行为几乎沒有任何变化 
不过到现在我还不知道如何清楚的解释这样的感觉。 (used adjective when it should be an adverb) --> 但到现在，我还不知道如何清楚(地)解释这样的感觉 
我想吃巧克时，身体似乎自动地反应 (missing the modal verb 'would'(會))--> 我想吃巧克时，身体似乎(會)自动地反应
而连吃巧克力以前我都感觉到很满意 (less effective word: '而连' (and even) should be replaced by a stand alone common word '甚至') ; (ambiguous word: '以前' can also mean 'previously' If you meant 'before' it should be 之前 or simply 前) and missing the modal verb 'would'(會)) --> (甚至在)吃巧克力前我都(會)感觉到很满意
这是我现在的解释，可是肯定是不准确的。(less effective word, '准确' mainly means accurate/ precise, for the meaning of 'correct' it is better to use '正确' ) --> 这是我现在的解释，可是肯定是不正确的。


Overall you've done a good job.

PS. Try to avoid run on sentence. You can break a long sentence up with commas, like in my suggestion here 不过到现在我还不知道如何清楚的解释这样的感觉 --> 但到现在，我还不知道如何清楚(地)解释这样的感觉 Just like taking a short pause in speech