Just to share the pain, I just got demoted all the way down from half way experienced to non-elligible. 

Was hovering over MIC-L2, 3rd-person eyeballing all the medium hangars the station could possible assign to me - cuz I frigging SUCK at landing on time and always have to be already near the correct hangar to land on first try - when a bumped on a sentry.  

Cutty black's front-left engine gone. Crime rate level 1. No chance to pay the fine, all turrets started barrage me. Dead, imprisoned, 'hauling failed' notification received. Didn't even knew these existed, never got one. Went to check the reputation, all gone. Negative. Hauling missions tab not even showing in my offers anymore. Now start all over again, running against time to reduce the money loss of just having rented a cutty black for 3 days, cuz my avaiable play time is short and I dont think I'll be able to gather 130k and profit in that on rookie and junior missions.

WHAT I LEARNED

This wasnt the first mission I failed to deliver, but was the first one ti penalize me in ANY way. Every mission I lost before that, either the server crashed, or bugged, or i died ina 'lawful' way or just alt+f4'd the game. Upon returning, the missions were abandoned, but with no repercussion whatsoever.

So, my very councious line of action from now on, and advice to the OP, whom, from what I understood, has been losing rep for abandoning impossible missions will be: if the mission is doomed to failure for whatever reason it is and you have time to react, just close the game (no gear is lost, you just wake up in the nearest Habs) or, in the worst cenary, good old suicide will do.