There's a quote I love, the full version is a bastardisation of quotes from William Hutchison Murray and Johann Wolfgang von Goethe, but it's about the importance of starting things - not completing or succeeding - but beginning. It ends: "Anything you dream you can do, begin it. Boldness has genius, magic and power in it. Begin it now!".
Things may not go to plan, but the unexpected throws up experiences and opportunities you had never dreamed of. I didn't get into Oxford the first time. I was absolutely heartbroken. Instead of going anywhere else I took a year out and reapplied. I wish I'd had some kind of framework for that year out, instead I worked in a Virgin Megastore. But looking back it taught me a lot, and meant my university experience was different, not worse. In the end, your grades aren't as important as the people you meet, and you can meet them anywhere.
It's so much worse to regret something you never did. It's often worth running through your fears to their logical conclusion to help disperse them. One footnote - if life has taught me anything it's to trust the shy people. Popularity means a lot of people like you a bit, you have broad appeal. But who wants broad appeal? Interesting people are always a bit niche. Remember what Steven Patrick Morrissey said: "It takes guts to be gentle and kind.".
At uni I met a lot of people I had nothing in common with. Some were very clever, some very rich, some very sporty. Some of them became my best friends, but not at first. Having things in common isn't always the best start to a friendship. I'd stick with it! Also, try to chat to people when they're on their own. So many people feel they need to perform in big groups.
