Conversely, I personally believe that using some part of you however small, to write a character is quite the benefit, actually. It provides a base for inspiration and personality and is far easier than trying to profile something or someone that's entirely separate from you, and it assists with developing a story out of it should you choose to. Walk before you run and all that. Could be an event that shaped you, a past detail you're not proud of, or maybe something you are. Somebody you met, a hobby etc. Besides that, inspirations from things or people you enjoy is also a big help, just be careful with how much you take from it.
As for getting into character...I've always had a big imagination so luckily it's been pretty easy for me to escape the real world and immerse myself in something that isn't mine, or me. Freelancer was actually somewhat of a catalyst for that when I got into it as a young'un. Space was always very cool to me. I was a hell of a daydreamer growing up (still am, even at age 30) and would always create scenarios in my head which were always inspired by games I was playing at the time, so putting that to some practical use via RP is fortunately quite easy for me. Certainly no expert though as I almost never write things down as a permanent note and therefore head-canon tends to forget details here and there.