In The Alchemist, what effect does the merchant say Santiago has had on him?

In Paulo Coelho's The Alchemist, the crystal merchant is a man who once had many dreams, as does Santiago.
For all of his life, the merchant wanted to go on a pilgrimage. However, work and responsibilities kept him so busy that the dream faded, and that old wish has become a source of sadness and regret for the merchant. 
One day the merchant takes Santiago aside, and they smoke the hookah and talk.

Before you came, I was thinking about how much time I had wasted . . . It made me very depressed. Now, I can see that it hasn't been too bad. The shop is exactly the size I wanted it to be. I don't want to change anything because I don't know how to deal with change. I'm used to the way I am . . .
You have been a real blessing to me. Today, I understand something I didn't see before: every blessing ignored becomes a curse . . . You are forcing me to look at wealth and at horizons I have never known. Now that I have seen them . . . I'm going to feel worse than I did before you arrived. Because I know the things I should be able to accomplish and I don't want to do so.

Santiago enables the merchant to see personal success that he never before recognized. However, Santiago's presence has also allowed him to understand that he does not know how to deal with change, something that is often difficult for many people in the world to face and accept—in fact, it can often be paralyzing. It is the merchant's unwillingness to change that will forever alter the way he sees the world and his place in it.
It is interesting that he considers Santiago's presence a blessing even as he comes to understand the consequences of ignoring a blessing. Perhaps human nature drives him to be content with his limitations as opposed to his opportunities. It is sad, too, that he allows his stubbornness to control his fate. Even Santiago struggles with settling for less than what his dreams had once guided him towards.
However, whereas Santiago ultimately decides to continue with his quest, the merchant acknowledges his unwillingness to change and his acceptance of the disappointments that will accompany his choice.
Whereas Santiago's quest is reignited in him, the merchant—even with his new self-awareness—chooses to leave things as they are. His desire to resist change becomes stronger than his desire to achieve his old dreams. While knowledge drives Santiago, fear of change appears to shut the crystal merchant down. He is sadly resigned to the way things will be in his life from this point on.