Every day people turn down opportunities because they will not know anyone where they could go. Do not let that stop you. For example, I am currently sitting in the Airport at my gate for my flight to go to Boston. I have never gone to Boston and I do not know anyone who is going to Boston. I was accepted into a conference there that I know will help me to further my career and my education, so I am here.
Being given opportunities are not always an everyday thing, so the small hiccup of now knowing anyone on the flight should not stop you from taking advantage of those opportunities. Some of your best friends may come out of those times because you are not latched onto people you know, and therefore are more open to meeting and becoming friends with others. There is no reason you should walk out of a room you have spent over an hour in without making a connection. That connection could be someone you add to your LinkedIn network and never contact again, or someone who you may keep in contact with and continue to pursue that relationship with. It does not have to be a lot, but make sure you are making those connections. When people say "connections are key," they are not wrong. The more connections you have, the more opportunities you will hear about and the more success you will ultimately have. Being able to tell a potential employer that you know someone they know who can vouch for you is always giving you a step ahead of anyone else who is applying for that job. Without that connection, you are just another nobody who all they have to go off of is your resume. That resume may be great, but they do not know how you are as a person. Are you approachable? Do you have a good temper? How about your work ethic? Having someone to vouch for even one part of your personality shows them that you are someone they will want to hire and work with in the future. Make sure to have those people in your life who will vouch for you.