I think 'Heaven' is a state of mind. If you were at peace before you die and have been a good person, then eternity will be a wonderful dream but if you were troubled and a bad person, it will be an eternal nightmare.
Here's a little story I was told many years ago about Heaven and Hell. I think it's a great parable:
A man dies and meets St. Peter, who asks if there's anything he'd like to do before entering Heaven. He replied, 'Yes, I'd like to see Hell.' St. Peter takes him to Hell and, to the man's surprise, it's a lovely room with a huge banqueting table, full of wonderful food. However, all the wretches sitting round the table are starving because, instead of hands, they have 2 meter-long forks so can't get the food into their mouths. He then goes to Heaven and finds the exact same room, with wonderful food on the table. To his surprise, the people there also have 2 meter-long forks instead of hands. But they are fat and happy. When he asks St. Peter how this can be, St. Peter replies, 'They have learned to feed each other!'