Hmm.. that is an interesting subject. I did have that problem in the past, but now i've gotten over it. And I think I know the problem.
Do you find that you revert back to haymakers and such because of the fear and stress in the situation? Because that may be why.
My concept is that it doesn't matter how technically good you are, how hard you can punch, or what you can do in the dojo.. it doesn't matter if you can't handle the fear and stress that is inherently found in real fights.. because it will go out the window.
You first have to be able to deal with the fear and stress before you can perform properly. It took me a while of getting real experience doing security before I could perform alot of the stuff I had trained, simply because I started to learn how to deal with the fear and confrontation from experience.
But I wouldn't recommend actually getting the experience as a way. What I recommend is to introduce a bit of this into your training. I have started this with a few people i'm teaching and the results seem good so far.
So of course you first drill the techniques normally with no resistance or stress, but then you start to introduce it slowly and build it up..
For example.. a few of my current ideas, taken from different places and also added my own things.
Level 1 - Attacker gets right up in your face in different aggressive poses.. the defender just stands there at the moment and feels the discomfort (at first you will feel discomfort, that is good)..
Level 2 - Attacker adds dialogue ("fuck you, what you looking at" etc..) and pushing, a little contact, to make it a little more stressful.. defender still doesn't act and feels the discomfort and stress.
Level 3 - Now the defender will take up a passive stance and attempt to talk the attacker down. One of several things can happen. The defender feels he isn't able to talk it down and pre-empts the attacker. Or the attacker will throw a haymaker off either hand and the attacker blocks (at beginning levels, just blocks it, later on will continue the defense, depends on your level of experience) or the attacker will just walk away because he has been talked down.
It helps to actually get into the mindset.. as the attacker I like to close my eyes, imagine a situation where I would be fired up or use a past one and really try to feel it, then encroach on the other person. As the defender I like to stand with my eyes closed, until there is physical contact such as a push, to replicate going from maybe walking down the street unaware, to some guy getting aggressive all of a sudden (though you should of noticed him earlier - awareness).
Now I could type more on this.. but that gives you the basics and what I am talking about, how I have built this is asked myself a certain question "how can I teach people to deal with the fear and stress in a fight with training" and built off that.
So mix these drills up, add to them, try new things.. add tackles, clinches, straight punches, grabs or whatever..
Basically I feel the important thing with training is to learn to think for yourself and take basic building blocks and build from there.
Hope that helps.. with a little creativeness you can do alot with what I have typed so far.
Any comments or questions would be good.
-Ben