Hmm, this seems to be going where I wanted it to go, thanks for trying even though I was apparently unclear at first :)
So, first of all, I think, like others have mentioned, there's no such thing as an objective hell or heaven. Even if there is, that's not really what this thread is about I'd say. After all, I don't think you can practically change anything objective with your mind that's not in your mind. Second, hell is just a matter of saying (for me). I'm just talking about (really) bad experiences etc... Likewise, heaven would be good experiences, happiness etc.
So, can you manipulate yourself in such a way that things that are generally considered bad experiences, preferably by you as well (at least before you learn how to change them from hell into heaven, again, as a matter of speaking), make you happy?
I think that it's definitely possible when it's more of a small annoyance, for example, I'm always annoyed by rain, but today I had to go out in the pooring rain to buy fish, and I just told myself as well as everyone else who asked (a lot of people surprisingly, I must have looked quite happy :P) that it was nice and refreshing. I really enjoyed the rain, until I went inside really, since at that point I was pretty soaked, and when the rain stops falling on you, there's nothing refreshing, you're just soaked. Of course that's a very small thingy, but it's about the concept. I don't know if you can change a really bad situation into something you can enjoy with your mind, but I think it's definitely possible to cheer things up a lot with just your mind. I'm not sure if it's comparable, but I think I'm in many if not all ways happier than some people who have a better life in many if not all ways. I feel like I don't need a reason to be happy most of the time, and it takes a really good reason to make me unhappy, or even just not happy. And even then, it sometimes takes a while before I get unhappy. I remember my uncle died, about 9 years ago now, but I wasn't sad the moment I heard it. I remember that back then, as a fairly little boy, I already had a really simple philosophy of "just be happy". So I just smiled and such (not in a disrespective way, more in a supportive "cheer up!" way, or at least that's how I meant it back then, but I don't remember it good enough to know if it actually worked :P), right up until I had to bring some holy water (or however it's called in English? I don't have a Christian background, but my uncle did, and my family wasn't exactly anti-Christian). I cried right there, and spilled most of the holy water. And about ten minutes later I think I was done crying. Even when I was crying, I didn't feel unhappy, just sad. I have had more similar stuff, some more recent, although I must admit it becomes harder the older I get to stay happy when bad things happen. It's definitely a skill or trait or virtue or however you want to call it I'm trying to keep with me though. Does anyone recognise this? Is this some obvious behaviour or something? I'm not trying to imply I'm special in that way or anything, I honestly don't have a clue if this is unusual. I do think it's a good thing though.