There's the common image of the writer who closes themselves off from everybody else to focus on their work; and I have to think, can their writing be that good? I think human interaction and life experience are equally (if not moreso) important to the writing process as being good with grammar and the ability to string words together in a nice way. Curiously, I don't find my fiction writing to be quite as stilted by this as my blogging is (probably because my blogging is directly related to what happens in my life, whereas with fiction that's not so much the case). But I notice that, when I'm out doing things, I come across lots of stimulus which prompt me towards all kinds of ideas and I don't have that so much now.
So, I guess what I mean to say is that, as much as it may be important to have time alone in order to focus on the actual craft of writing, you mustn't underestimate the importance of all of the other things you do. In the end, I think of writing as a reflection of a person's thoughts, and if they don't have much to think about, their writing may not be all that exciting.