Humans are easily influenced. If you think yourself immune, you are either lacking self-awareness or are in denial. This is not to say that influence is inherently bad. It can be a nurturing or destructive force, depending on the source.
Take care with who and what you let enter your life. The friends we make, the media we consume, and the communities we join all create the environment of which we are the product. You must have a strong set of beliefs and principles that enable you to judge whether an influence is healthy or not. If the answer is no, ruthlessly cut it out of your life. The bad has no right to your time.
You must be honest with yourself about your surroundings. Who is influencing you? Does this influence improve your life? Is it making you a better or worse person? Does it conflict with your nature? What about your purpose? Let these questions shine a guiding light on your life.