The Gospel of Thomas is controversial and much of it is open to interpretation.  One thing that is clear from several of the sayings is that Jesus, through Thomas, is advising us to know ourselfs if we want to advance spiritually.  We need to know ourselfs and know where we are starting from if we expect to get anywhere.
    An old story probably everyones knows is the one about the carpenter who is hired by a wealthy man to build a new home.  The carpenter has a good reputation but decides in this case, the wealthy man can be taken advantage of as he will be able to afford to make repairs later.  So the carpenter builds a good looking but shoddy house with below standard material and workmanship.  When he finishes, the wealthy man informs him that he doesn't want the house for himself, the house is for the carpenter.  A gift from the wealthy man for the great work he has done over the years.  
    The moral of that parable is that we are all building out own "house".  We all create the life we live to a large extent by the choices we make, the things we do, and even our thoughts and dreams.  So if you want a better life in this world and want to develop spiritually so you will be ready for the next, than you have to examine yourself and decide what your faults are and how best to correct them, and not just one time, but regularly.  Ask yourself questions like:

• "Why did I get angry today?  Why did that guy make me angry?  What does my anger at him say about me?"
• "Why don't I have the job that I really want?"
• "Why don't I pay attention when my spouse is talking?"
• "Why didn't I do that job I promised to do?"

Those are some examples and the real questions and answers will differ for each of us.  The idea is to find out why you are not the person you want to be and what you can do to fix it.  Of course, the first step is figuring out who you want to be.  For us older folks, it isn't so hard because we can look back on our decision  For younger people, I suggest you think about yourself ten or twenty years from now, looking back on what you are today.  Will you really be happy and satisfied with that person?  Are you heading toward your goals, or away from them? You have to be honest about it. It will be difficult at first, but is well worth the effort.