The verse, ‘Issachar is a strong-boned donkey, crouching between the borders, he bent his shoulder to the burden, and gave taxes from his toil’ means to say Yissachar accepted the yoke of Torah with all the weight of its toil day and night despite the hardship. This is like a rich diamond merchant who travelled to a far off country to buy goods and after using up the money he intended to buy with, was offered a large amount of merchandise for a small amount of money, so he used most of the money he had put aside for the trip home and travelled home in third class. On the way he met one of his rich friends who was shocked to see him in a freight car. When the merchant showed him the stones he bought for the difference in fare, his friend said, ‘now I understand why you did this, but your body is not accustomed to such hardships’. The merchant answered, ‘Indeed sometimes I regret it, but then I take out these jewels and see their beauty and value, the hardship I am enduring is completely outweighed by the pleasure I get from seeing them and thinking what I will buy with the money I get.’
That is how a person learning Torah should feel, that even though he gives up all the pleasures of this transient world, the pleasure and reward he will get in the world to come makes all the suffering seem insignificant. Although there are times that the difficulty seems too much, he should then think about the reward he will get for this hardship and realize that the hardship is nothing compared to the reward, and he will renew his learning with extra vigor.