The less you let it get to you, the happier you'll feel. Trust me, it gets a lot harder as life goes on--I have to worry about having enough money to go to college being COMPLETELY broke and unable to pay for the colleges I want to attend unless I get 4 jobs (at minimum wage--I've had to go through and calculate it) and then I won't be able to get my Masters at RIT meaning I'm stuck to menial labor jobs that pay only 20-25k a year, hardly enough to start planning for your future on. That is, if I don't get any federal aid, which I'm sure I will, combined with scholarships hopefully.
Just put it into perspective--your grandmother's upset: bad. Your dog is in pain: bad. You've got a girlfriend: good. Everyone thinks you made out with her: good (yes, repeat after me, good). You've got money: good. You've got a roof over your head: good. Life isn't that bad--it just seems that way. Even if you don't feel like it, adopt this attitude and just forget about all the bad stuff--doesn't mean you have to be happy (though it helps), as long as you aren't sad, things tend to get a lot better a lot quicker than you'd think.
Hope you could get something out of my post.