In chapter 4, volume II of Frankenstein the creature was still in awe of the cottagers, and he fully expressed his admiration towards them during his moments of reflection. He liked their looks, their actions, and even the utterances that later he identified as words.
The creature was in a state of bliss. He was connecting emotionally with the family and he created a fantasy in his head in which he was one of the De Laceys. Shortly after he had begun to experience those feelings of love and affection, he had the horrid experience of seeing his reflection in a pool of water.
In the monster's words:
... but how was I terrified, when I viewed myself in a transparent pool! At first I started back, unable to believe that it was indeed I who was reflected in the mirror; and when I became fully convinced that I was in reality the monster that I am, I was filled with the bitterest sensations of despondence and mortification. Alas! I did not yet entirely know the fatal effects of this miserable deformity.
The creature's words demonstrate that he suffered two huge disappointments: First, having to break from the fantasy world that he had created, in which he was a part of the De Lacey family. Second, having to accept that he was a far cry from what he would have wanted to be.
It must have been a devastating blow for the creature to know that he possessed the needs, wants, and desires of a human and yet he had to live hiding from humanity itself. The reflection in the water was more than just the monster facing himself, but it also represented the creature's sad acceptance of his reality and his destiny.
In Mary Shelley's Frankenstein, the creature has never really had the chance to see what he looks like. He has been scorned and rejected by society, even by his own creator, but does not grasp the significance until he has had time to watch the DeLacey family, and see their beauty: within and without.
I had admired the perfect forms of my cottagers—their grace, beauty, and delicate complexions: but how was I terrified, when I viewed myself in a transparent pool. At first I started back, unable to believe that it was indeed I who was reflected in the mirror; and when I became fully convinced that I was in reality the monster that I am, I was filled with the bitterest sensations of despondence and mortification. Alas! I did not yet entirely know the fatal effects of this miserable deformity.
In reading this passage, we learn that the sight of the creature's reflection in the water at first terrifies him. We can assume, this would be the case with anyone who has no concept of a mirror or "reflection," who might be mesmerized by the sight. The creature is particularly intelligent, and soon he realizes that what he sees is his own face. He responds with a sense of abject sadness and "mortification" (or shame, humiliation, embarrassment).
The last comment the creature makes in the passage is an example of foreshadowing. He has spoken of his hopes to make a connection with the DeLacey family, which he so admires. His physical appearance will make this impossible.