Leaving this plane forever isn't quite that simple as finding your life's purpose. When you die, you do go to a plane that is eternally bliss and harmonious that could be considered heaven, but we end up coming back to this plane because we get bored up there and seek to learn new experiences this plane has to offer us. The experiences may come through pain and fear or it may come through love and happiness. It all depends on what you are trying to learn and the best way for you to learn it. In order to leave this plane for good, you need to ascend to the point in which this plane has nothing left to offer you; you have learnt everything the earth has to offer you. That can take thousands to even millions of incarnated lifetimes on this planet. It all depends on how fast you can learn what you sought. Forever leaving this plane is known as gaining spiritual enlightenment or reaching a state of nirvana.
Although you may not be consciously aware of your purpose, your higher self is constantly warping the reality around you to bring the purpose of this point in your life to you. There are certain lessons that take our whole life to learn while others only take certain phases of our lives to learn. You consciousness creates your reality. When you are focused on learning the lessons this world has to offer you, it will help move the process along more harmoniously. You want to bring harmony into you life where ever there is discord. You want to remove any undesired emotional responses certain situations may stimulate by bringing harmony to that situation. It will help move the situation along by having the intention of harmony in your heart instead of the intent of conflict. These situations occur to help you remove negative attachments you have so your soul can be free from the chains that bound it. This world merely acts as an illusionary state to help us with what we truly seek, experience. Everything that happens here is quite real, but only acts as a means to an end. We enter into a deluded state here because we seek to find the answers through our experiences here for we already have all the answers we seek in our eternal state. The further you develop spiritually, the closer you get to your highest self, your eternal self.
We are spiritual beings seeking a physical existence, not physical beings seeking a spiritual existence. We have all the answers we seek in life, the only thing left is to create a stimulation that can help us recall what we seek. And remember, spiritual growth is not obtained through the destination but rather through the journey itself.