If things are going well and it is nearing lunch time, there is often the temptation to keep working and take a late lunch. This can often be a bad decision.
If something goes wrong and prolongs the trial, it becomes much more difficult to maintain the level of concentration needed to not make serious errors on an empty stomach.
You may be perfectly allright but those working with you may have health concerns which require eating of which you are unaware.
In any case, it's always a good idea to have a little something along to munch on if you do succumb to the temptation to delay lunch.