I remember thinking up this midrash on my mission, though I didn't know it was a midrash at the time.
Matthew 25:18 But he that had received one [talent] went and digged in the earth, and hid his lord’s money.
This servant was rebuked for not trading with his talents and getting an increase, as the other two servants had, but in his heart he was resentful for the rebuke because he had, after all, worked harder. The first two had invested the money and let interest do all the work while they sat at home doing nothing. The last servant had traveled to the desert and found a hiding place away from the beaten track. He had dug a deep hole all by himself, buried the money, and replaced all the earth perfectly so no one would be able to discover the cache. He then had to go retrieve it when his master returned. It was all a laborious process, much more intensive than the passive "work" performed by the two servants who the master praised so well.
This scripture shows us that working hard is not the goal. Effectiveness is the goal. Magnifying your calling does not need to mean you stay up to all hours of the night putting together flyers for every class or planning who will read which quote or organizing every detail. We need to prepare, but it is not something to stress about or overdo. Spending time with friends and family, taking a walk through the woods, or reading a poem can be the best preparation for a lesson. Look for ways to let your efforts go farther--to gain the interest of the Spirit on your investment of time--rather than doing everything yourself.