He didn't specify how long he has used gear, the dose he used of those drugs ect. Let's say he's not some newbie that is just scared.
In this case a drug builds up in your system, we can agree on that. You start low levels of the hormone in your blood and the levels slowly rise until it peaks and stays at that elevated level assuming you continue with the same dose. At this point you see results in muscle mass as well as side effects like acne, and other estrogen related side effects or possibly other kinds of issues. But for someone like myself who is especially prone to severe anxiety, it may not take that long. The drug is in your system from the first dose. A couple of days into a tren ace cycle I start to feel edgy.
Granted, he seems to be exaggerating about it taking only one day. It may take more than that but surely not weeks. If he replies that he is newbie and he seems to just be scared then fine, but don't act as though anxiety is just someone acting scared. I'm not "scared" when I'm very anxious. Its a disorder that needs to be taken seriously and unless you have it then you should not be giving advice.