You're young, so that's in your favour for starters. Don't look at stats for remission, recovery etc - remember that older patients aren't able to go through some treatments. Dr Google is an idiot, so please avoid!
You are in the right place (I know it doesn't exactly seem like that now) and in good hands.
Ask lots of questions - learn about 'the enemy'. Ask about the treatment plan and what alternatives are at every stage (don't forget the question 'if I were your sister/daughter, what would you recommend/suggest?).
The treatment sucks - you will be tired and feek sickly. Do whatever you need to help yourself feel better. Hospital food is generally awful, so get family/friends/mumsnetters to do a rota of meal deliveries.
Do your nails, read trashy novels, learn a new language, gossip with the nurses... Keep busy, keep your mind positively active. Plan what you will be doing next month, christmas, birthday - don't allow yourself to even think negatively.
So many of us lot here have such experiences - first, second or third hand of this sort of thing, so ask away. You can, of course also swear, moan, cry or bitch as much as you need to. Theres always someone about for you.
Good luck - best of British - stay strong.