The first three tenets deal with the different kinds of actions we have when we interact with others: respect, kindness, and harmony. However, the fourth tenet shows how we carry out that task or action. And that is by being true.
Being true in your endeavors will help you gain others' trust and enhance your success. Whenever there is a task, you must put your heart into it.
Buddhism focuses on cause and effect. The saying, "no pain, no gain", means that we must put in our effort in all that we do, and that will definitely be positive for our future. This concept can also be applied to the fourth tenet. Be true to others and they will do the same.
If we respect our elders, we eliminate hatred. Being kind to juniors eradicates anger. Being in harmony and at peace with all sentient beings, we will become peaceful, honest, and sensible.
Everyone has as talent, no matter if it is in mathematics, art, sewing, basketball, etc. Even if you are not outstanding in a particular area, give yourself a chance before you begin to ponder, "Oh, I can't accomplish this. I'm not good enough. This is too hard." Give it a try, and you might just develop a knack for it. However, you must avoid cheating. All people have the same potential if they put their heart into what they do.
Follow all the four tenets and you will eventually become successful.