Ek nishtha or sincerity is like the lamp that shows us things exactly as they are without colouring or covering them with justifications. This is the first step. It is called mental honesty.
Once we see things as they are and recognise them for their true worth we have to act upon the indication given and the thing that is shown. Each time we act according to what we have seen to be true we grow in sincerity.
Next we have to develop it in every part, every action and also keep sharpening and widening the truth we can see in the light of sincerity.
Affectionately,
Alok Da