Life is decribed here as a steep mountain we have to climb over. It is hard enough to climb with just the necessary supplies in a backpack. However, he/she who tries to climb it with two heavy suitcases in hand, in addition to the backpack, will not be able to reach the top. They may well die before they are successful in their mission.
Why is it important to climb high? Because only the successful mountain climbers will enter Jannah.
What is the luggage that is weighing you down? It is your unnecessary involvement in the matters of this world, the things that will not count in your favour when your deeds are weighed in the Balance on the Day of Judgement.