I don't think it's good to "try to keep yourself positive", because by suppressing your feelings you may get yourself to feel even worse without noticing.
It's best if you try to defuse your stress, which goes best by either talking to someone about it, or by physical activities. It really helps a lot if you, for example, attend a boxing club. It relieves a lot of stress, physically.
I know that you can't always find someone to talk to from experience. I always try to distract myself with other things and listen to music that boosts my mood. Also working out is great to help your mood (and your health).
Good luck!
>>3I would be careful with that, because talking about your own problems makes a lot of people like you less, even if "only" subconsciously. Try to talk about their problems first, then try to talk about your own. Also be warned, because there are a lot of people who will talk to you about their problems, but not listen when you want to talk about your own problems. It's disgusting, but a lot of people do so.