All of the different aspects of service of Hashem need evaluation to see what is the correct way that a person should conduct himself so that his reward should not be cancelled out by his loss. Examples of this are people who stay late at night in the house of Hashem who must be extra careful to ensure that they will not fall asleep during the reading of the Shema and the morning services, and if they do not sleep at all during the day they might come to sleep during the evening services or during the Grace after meals, in each of which cases the loss is greater than the gain. Similarly, one who learns while dozing has worked for nothing and a small amount with correct concentration is better than a lot without concentration. This is comparable to that which people say that a miser tries to save one penny and in order to do so he spends four. So too is a person who tries to gain one extra good deed, but by so doing he loses many other good deeds. A person must always make sure that in the service of Hashem the extra bits add on to the basic service, and not that the extra bits destroy the main service.
One must also evaluate and distinguish between good and better. Examples of this are when learning as of course all learning is good, but he should choose a learning which fits with his own intelligence and with time that he has for learning. Examples of this are laws which are relevant for him at that time or the laws of the offerings which are very important before Hashem, or books of ethics and fear of Hashem. If he has time he should do all of these.
