Yes it sounds a contradiction but a good example is your preparation for a swing. You'll all sorts of actions you include as part of your habitual set-up but because they are automatic habits you'll invariably be unaware that you're doing them. For instance, many golfers tighten their jaw as they concentrate on the shot ahead. Sounds fairly tame but did you know the act of tightening your jaw will impact on your neck and shoulder muscles, that in turn, will interfere with your coordination. So at a time when you need to get all your muscles working as one to execute the swing, you'll be putting on the brake.
Unfortunately, your habits feel absolutely the right thing to do because you're used to the feel of these actions and therefore you won't start your swing until all the usual feelings are in place. So every time you play or practise you could be consolidating poor habits that are preventing you from becoming a better player. As the wise sports coach said, "practise makes permanent, not necessarily perfect!"
Have a go at the experiment in my ultimate golf fitness test to get an idea of what's involved. Also see Overcoming Problems With Your Golf Technique