Can my marriage be saved? - I might be a compulsive liar.?

I have been married for 6 and a half years and have on a pretty consistent basis lied to my wife to get out of trouble or avoid a fight. If I make a mistake she can be pretty hard on me. She makes me feel really foolish and treats me like I'm the only one who could make such a mistake. She has threatened divorce for a couple years now and I keep promising that things will be better. Well, a couple more years have ped and still I have not shown any improvement in my ability to tell the truth in those situations even though I really want to. I tell "white lies" like everyone else but, when I make a mistake at work my first impulse is to "own" that mistake. Why do I fear my wife's wrath? It is clearly hurting her and she is really, I think, very clinically depressed by the fact she can't trust me. Just the most recent example, my wife ripped the headlight off her van backing out of the garage. After trying to fix it once unsuccessfully I gave it another shot the next day. I hooked the light up and just had it sitting in the opening. I got distracted from that task and forgot to get back to it. ( My plan was to zip tie the thing back in). Needless to say that came back to bite me in the rear. the next day my wife called me to tell me the light had fallen out on the freeway and made a guy swerve behind her. I almost immediately told her I zip tied it in and it must have broken. Clearly a lie. And when she called me on it a few days later, as she knew I was lying too, I couldn't remember even telling her that lie. It seems I have a real problem here, at least in my relationship with her. I think this could be the end of a tumultuous marriage, but I am a hopeful person and I want to find a solution to this problem, before I put her through another minute of hell or I'm just doing it for myself, which in either case I think is a good thing.