In Parshat Vayechi we learn about the blessings that Yaakov Avinu gave his sons before he died. The blessings given to Yissachar and his descendants were that they would studied Torah. Just like a donkey faithfully carries its load, so too, the children of Yissachar would carry the "load" of Torah.
Yaakov Avinu was obviously praising Yissachar for his diligence in learning. There are other animals however that are stronger than the donkey and able to carry an even heavier load. If Yaakov really wanted to praise Yissachar he could have compared him to a horse, an elephant, or another very strong animal. Why did he compare him to a donkey?
Even though a donkey is not the strongest of animals it has an advantage over animals stronger than it. When a horse wants to rest, its owner must unload it. The horse cannot rest with heavy packages on it. The donkey, however, is different. When it walks, eats, or even sleeps it can still bear its load.
This explains to us why Yissachar is compared to a donkey. The work of the Torah is something that we always carry with us. Even on weekends or when we are on vacation we set aside time for Torah. The consistency and hard work of the donkey teach us how we must go about Torah learning.
In what ways can we improve our consistency to Torah learning?