Yesterday a post came upfront to Hacker News. To summarize:

personality is extremely flexible and heavily depends on environmental and social constraints

And the takeaway from the original NYMag article:

Really, though, the key takeaway here may be the optimistic notion that changing your personality is possible at all.

Why is it important? The majority of the people put themself into a category like, alcoholist or smoker or lazy. It turns out the social and environmental context are the biggest influencers in these cases thus the main goal for someone who wants to change drastically is to change the environment and community which he/she belongs to.

Unfortunately there are people with personality disorders, where the change is non-existent or almost impossible. In these cases the aim should be not to make worse the situation or just making slightly improvements in the long term.