Just to reiterate, the fact that you were offered Active Surveillance means you have a low grade cancer, but it still helps us to help you if you can put your PSA, Gleason (e.g. 3+3) and Staging (e.g. T2b) into your profile, together with any other information you have (such as how many biopsy samples contained cancer).
Actually, you don't have a time limit to decide, because you can choose Active Surveillance and carry on thinking about it, as you can switch to active treatment any time you like. (Some people find that Active Surveillance doesn't suit them mentally, and then switch to active treatment.)
The period during diagnosis and being told you have cancer is very anxiety generating, because this is all new to you, you don't know what to expect, and cancer conjures up images of people dying in a couple of weeks (which doesn't apply to most prostate cancer diagnosis, particular those caught early). Prostate cancer grows slowly in comparison to many other cancers, and sometimes it doesn't grow at all (in which case Active Surveillance can be a good choice).
For many patients, the anxiety can be at least partially resolved by finding out more about the disease and treatments - knowledge is power - as they say, and anxiety is in part caused by not knowing what to expect and having a feeling of having lost control of your future. Knowledge helps you to know better what to expect, and when you get to make your treatment choice, that's a significant point in taking back control of your future.