This brings us to the problem of Lay lines. If you have sailed to the lay line (do you understand that this is line along which a boat would sail to reach the mark, if everything stayed the same - only it doesn't). If you are hit by a gust and head up you, are sailing away from the mark. Even if you let your sail out the speed increase will rarely compensate for the extra distance you have sailed over someone who tacked below you and is now able to use that extra pointing ability brought about by the stronger wind in the gust.
Then again when it is shifty, as it was last week, being on the lay line means that if the wind changes direction you are not going to be able to make use of it. If it lifts you you will have to ease sheets and reach into the mark. If it heads, you probably have to keep going into it, so that you can get to the mark. If you tack on the header, as you should, you will soon be overstanding the mark and will only have had the advantage for a very short time.
This is why - unlike novices who fear tacking - you do not want to go out to the layline or go upwind in large tacks. Keeping to the middle of the course gives you flexibility and enables you to use shifting or varying winds.