I believe that other things that may influence behaviour other than the environment (see Change the environment to obtain what you want) are the: Ways how you do something If we do something in a way that it is too difficult or complex, it is likely that we will avoid that. Why we do something. The purpose why we do something influence our behaviour. If we have a strong purpose is likely to engage in particular behaviour and viceversa.

Our behaviours (see What is the relation between happiness and behaviour) Satisfaction of the three basic psychological needs (see Self Determination Theory and What contributes to well-being) Related Questions: Related Topics: What is the relation between happiness and behaviour What contributes to well-being Happiness References Introduction to Self-Determination Theory | University of Rochester by Coursera

In the context of the following topic Change the environment to obtain what you want, the environment is everything that is around you with which you interact and that may influence your behaviour. Related Questions: Related Topics: References

Happiness is a gap between what we want and what we reach in life. What we reach in life is the results of our actions. Our actions depends by our behaviours. Therefore what we reach in life highly depends by our behaviours. Therefore I believe happiness highly depends by our behaviours. Related Questions: What happiness depends on Related Topics: References

Our behaviours are conditioned by the input we receive from the environment we live in because this is the way our brain works (see Brain). Related Questions: Related Topics: References Brain

I think it is because the principles described in Principles of Getting Things Done reduce the time to process things we have to do. In fact having all the things in one place reduce the time to search items to do. Moreover, standards are a way to go fast because you have not to think anytime how process something. Related Questions: Related Topics: Principles of Getting Things Done References