I define realism as dedication to thinking clearly and carefully about your goals, and not jumping to conclusions. It emerges from the combination of carefulness, lucidness, introspectiveness, and moderation.
Without introspection and moderation, you might end up settling for something that seems safer than what you really want. On the other hand, what you think you really want might not support well-being, hence the importance of lucidness and carefulness.
"The desire for imaginary benefits often involves the loss of present blessings." → Aesop