One of the greatest things that God has given us, aside from the promise of eternal life, His Son (who died for the forgiveness of our sins), and basically everything else that we experience, is our free will. Whatever circumstances we walk through in life, we have the ability to make the best or worst of the situation. It's because of this gift that, as Catholics, we're responsible for building heaven or hell on Earth. There are tons of interpretations of how, where, and when we get to experience heaven, but I subscribe to the idea that our time on Earth is meant to build heaven here and now, not hope for it someday later.
I once had heaven and hell described to me like this (by Fr. Bohdan Nahachewsky) which I think illustrates this idea perfectly:
Imagine you're sitting at a huge banquet table with a giant pot of stew in the middle. This is the most delicious stew ever made, and everyone around the table is drooling over the smell. Since the banquet table is so large though, the stew is very far away from you in the centre of the table. There's no way to reach the stew except by using one very long-handled spoon set on the table. This is heaven.
Some of those seated at the banquet table (those who have sacrificed all their lives and done good deeds and righteous acts) pick up the spoon and try to feed themselves with it. "There has to be a logical way to feed myself", they think. "This is my reward for being such a good person during my life. I deserve this!" The problem is, that every time they try to come up with a solution of getting the stew to their own mouths, the stew falls off the spoon. It doesn't matter how many times they try, how quickly, or how carefully. It always seems to fall off. Some of them may be lucky and get a taste of the stew through desperate acts like turning the spoon into a catapult or trying to eat scraps off the table left by their neighbours, but it just leaves an awful taste in their mouths. Pretty soon they decide the stew isn't even good or worth all the trouble. So, they sit there frustrated, hungry, and weak. Adding insult to injury, they look around the table to see others who are fat and happy and enjoying the delicious stew! Which makes them feel even worse.
You see, the fat and happy people around the table have had no problem with the way the table is set. They find no challenge with the distant stew or the very long spoon. One picks up the spoon, scoops some stew, and feeds his neighbour. Then another does the same. And another. And another. Pretty soon, all those willing to share the stew are fat and happy. They think "If this stew is even half as good as I think it is, I should share it with everyone so they can taste how good it is!"
The difference between heaven and hell can be as simple as your attitude.
I love this description of heaven and hell because ultimately we are in control of our experience. In the analogy, all of the people at the banquet table are given the same circumstances: a huge table, a distant stew, and a long spoon. It's not like being smarter or stronger gives anyone an advantage over the others. It is a level playing field and all the participants have the same opportunity to create their own heaven or hell. This is different from our Earthly lives in that we actually do have different circumstances. It's not a level playing field for everyone. Some may be battling silently with demons they don't know how to face. Some may be plagued with the pursuit of getting ahead of others. Some may seem to have everything going for them and not a care in the world. At the end of this life, what matters is your spirit.
Spending your life sacrificing and trying to perform righteous acts to someday be allowed in God's presence can be a tricky thing. Are you pursuing these acts and sacrifices for the good of others or for the promise of some kind of reward later? At the end of your life, will you be at the banquet table thinking you deserve the stew, or will you still have the heart to serve others first? We're in God's presence here and now and we have the obligation to work to make life on Earth, Heaven on Earth.
I think one of the biggest factors in creating Heaven on Earth is that we bring others along with us. We need to work together to create a community of like-minded people who want to share God's love and have a heart to serve. If that seems hard to do, seek out counsel with those you admire. Ask to talk to your parish priest. Read the Bible. Pray.
At the end of the day, God is the architect who came up with the plan, but it's up to us to build His Kingdom and bring as many along with us as possible.