"But, brothers, when we were torn away from you for a short time (in person, not in thought), out of our intense longing we made every effort to see you. For we wanted to come to you - certainly I, Paul, did, again and again - but Satan stopped us." NIV translation
Paul describes how when they were apart he tried over and over again to get back to see the Thessalonians. He says that it was Satan that prevented it. Some may read this passage and say "how can that be" and "isn't God in control?". Just as in the book of Job, God is in control but He allows Satan to roam the earth for a time and to have some power. It does not diminish God or His power and He uses it for the good of those that love Him.
"For what is our hope, our joy, or the crown in which we will glory in the presence of our Lord Jesus when he comes? Is it not you? Indeed, you are our glory and joy." NIV translation
The only things that we are taking with us to heaven are the people that we tell about Jesus. That is why Paul traveled and shared the Word and that should be our reason for everything that we do.
That is what Jesus was talking about, in Matthew 6:19 - 21, when He spoke of treasures in heaven instead of treasures on the earth.