Take All Games Seriously - How Even GMs Throw Games Away

Like most players in the 2300 rating range, I have a very good scores against weaker Masters, Experts, and anyone rated below that point. At the same time I have mostly mixed losses and draws against International Masters and Grandmasters in my tournament games. 

The occasional time I can hang with a Grandmaster, tends to be the occasional game when they don't take me seriously. Anyone playing the opening unnecesarily quickly is handicapping themselves, which can make any game complicated, or even lost before the proffesional player has started concentrating. 

Here are a couple of games that demonstrate my point. Admittedly, both opponents were International Masters at the time, a few months prior to gaining the Grandmaster Title.

My opponent's mistake in the next game gave me a big advantage, although the stronger player managed to hold on  due to a couple of my mistakes later on combined with ingenious defense on his part.

Conclusions:

It's OK to play the moves from your preparation quickly in order build a time advantage, but it's worthwhile to concentrate as soon as you leave your prep. Otherwise you can quickly get in trouble that you might not be able to climb out of.