We all know that only by much searching and mining, gold and diamonds are obtained, Similarly if we dig deep into the mine of our soul we can find every truth connected with us and will understand that we are the maker of our character, the molder of our life, and the builder of our destiny.
It is like 'PDCA (Plan-Do-Check-Act)' cycle. If a man analyses his thoughts in the light of Knowledge and Experience he has, then he will allow only Good thoughts to remain in his mind. This is possible only by practice and investigation.
By doing this he will promote the Noble thought hidden in his mind and one day he will become a noble person. PDCA cycle is scientifically proven method and there is no element of doubt
This is what james Allen has referred as 'He that seeketh findeth'
Finally, your Character is Sum total of your Thoughts, but Good thing is that you can change it my changing your Thoughts