There was a time in the past, many years ago, that you did not have the things that you have right now. You may have been just a rookie of life, starting to take on responsibilities and just beginning to work towards your goals.
During that time in the past, you could have only dreamed about being where you are now. During that time, you had a certain set of beliefs, a certain set of excuses, a certain set of complaints about life.
Fast forward many years to the present moment, when things are better and when you have made progress towards your goals. Is it logical to keep on acting the same old way at the level you are at now? No.
We must learn to improve our beliefs, remove our excuses, forget our complaining. These old ways are the relics of the past, and holding on to these will keep us from getting to our future.