The Pros and Cons of Me

I have, possibly mistakenly, begun a novel in which my main character is based on myself.  Of course she's not exactly me because the events that are taking place are entirely fictional.  But the thoughts, feelings and insecurities are largely mine and the environment in which it is all playing out is familiar due to it being a revamp of my alma mater. 
Part of me fears that this may be a huge mistake.  Last year when I was writing in the fantasy genre I had a lot more freedom to do whatever would fit with the story.  The kingdom in which everything was playing out was based only vaguely on preexisting ideas so if I wanted something particular to happen I could make it happen regardless of how ridiculous it might be.  (I.E. ignore the laws of physics, make up ridiculous laws or norms, change the physical appearance of anyone and anything to make it fit my story.)  The characters, although mostly humanoid, had inhuman abilities and used magic so that allowed for just about anything to happen.  And because I wasn't operating in anyone else's map I could change the rules at any time I wanted.  Long story short, it was easy.
Now, in a world based largely on my own past with a character based largely on me, I find myself thinking "That would never happen" or "That's ridiculous".  This, needless to say, is not helpful.  Having to remind myself  that "No, it's your story, you can do whatever the hell you want" slows me down and with only 26 days left that's not good.
Also, I've picked a far more serious genre to work in now.   Not because I purposely wanted to challenge myself but because that's what the story is.  There are moral and ethical issues she's struggling with, there are problems she's facing (and they're not the fun 'this crazy wizard is after me' kind-of problems), and there are some pretty serious questions she's gonna have to answer over the course of her development.  It's valuable, don't get me wrong.  But it's a lot less fun than writing about magic and wizards and other crazy stuff like that.
The other problem?  My main character, who as I already said is based largely on my own past, has familiar feelings, thoughts, insecurities, etc.  These are based largely on real memory so I find myself spending a lot of time in those memories.  They weren't pleasurable then and they're definitely not pleasurable now.  They're downright depressing in a lot of ways and I find myself needing to remind myself that that's not my life.  I'm not alone (romantically) anymore, I am a hell of a lot more secure in my sense of self, and I have at least a vague idea of what I can reasonably expect out of life.  (The main character's career situation, unfortunately, is striking a very painfully familiar chord with my current status.  Oh well.)
I am hoping that these similarities will serve for good writing, and not needless suffering on my part.  But it is definitely a challenge to stay grounded in my everyday life while I spend so much of my free time and thought on this story.
There is one positive I've noticed, though.  Since my character is so familiar I can easily recognize what is missing for her.  Specifically, while driving home this afternoon, I had the revelation that she is in desperate need of a wing-man/co-conspirator to keep her grounded.  If it was nothing but her own fantasy world things would go very bad very fast (much like if left with nothing other my own thoughts I tend to deteriorate very quickly).  She, like me, needs somebody to run all these crazy thoughts and ideas by in order to be able to do anything useful.  My story arch, up until this revelation, did not involve a wing man.  It was a one-woman show and I can easily imagine it going very poorly for her and for me.
But with an outside voice to be reasonable, logical and challenging my character can be clarified and forced to grow in a way that she otherwise wouldn't be.  And I think that's going to prove to be an important part of her journey, just as it was and is for me.
Now the big task for me, I think, is to make that voice in my head that's saying how something I want to do is preposterous or focusing on a ll these negative memories from my past shut the hell up so that I can be creative and have fun in spite of serious subject matter.  Because otherwise there's no way I'm gonna make it to 50k words.  Wish me luck!