[ModusOperandi]

English is a very quirky and overwhelming language.
If your main goal is to be able to get by in your day to day life without much of a hustle then the answer is yes. You can definitely learn it by yourself. (read novels, have a dictionary handy, watch movies, listen to music etc.) It is entirely possible if you're dedicated.

Do not underestimate the power of a "good" teacher though.

Take me for example, English is my third language. I started by learning it independently but when I started taking classes I noticed the overwhelming difference from what I thought I knew and what I was eventually taught...not to mention the pace at which I learned it all. The difference was night and day. I was completely humbled.

I guess what I'm trying to say is that, you can learn it by yourself but in the end you'll be limited to yourself. Its probably best to widen your horizons and seek the aid of someone who can magnify and expand on what you know.

On a side note, I feel a bit like a hypocrite right now considering that I'm trying to learn Japanese by myself lol.