As with any kind of relationship, your social circle is reflective of the relationship you have with yourself. Remember, you attract what you are being and giving out, so if the people in your world are negative and unappreciative, there is a vibration in you which attracts them. The way to change this is to either change what you believe about human nature (and start attracting the types of people who reflect a better belief) or change how you feel about yourself. Reality always follows self-image, and if you are appreciating yourself and paying attention to your positive qualities, then you will start attracting people who appreciate you. They will be biting your bait (your positive vibration) and acting accordingly.
And of course, visualise yourself each day, in social situations with the kinds of people you would like to associate with. Visualise a variety of scenarios too (from 'behind your own eyes' so to speak) and give the Universe some creative leeway in what it sends you. Have fun, use your imagination, and remember to do this for a few minutes each day.