There is a big difference between talking about a thing and doing an action. Talking is only a mental activity in which one has to go on putting argument and counterargument to somehow justify what he is saying. To others it may look as if the task is completed. Yes, apparently the verbal task is completed but not the real one about which there was such a long discussion.
When people really start some action then they see that there are many difficulties and obstructions and at every step there are if and buts and a number of decisions to be taken. So whether they are discouraged or are not capable of doing that, they simply leave it midway and task is incomplete.
Many people talk very casually. They are not only indisciplined but ignore their promises and commitments often. They do not take anything seriously but on the contrary, they talk as if they are the most sincere people on earth.
We have to take the verbal communication of these people with a pinch of salt because the next day if you ask them about their yesterday's promise, they will simply be showing their ignorance and may even resort to - 'Oh! Did I say that'. Most of the talkative people are like that.
So, there are a few people who are not like the above and honour their words and it should be our endeavour to have friendship or relations with them only.
Knowledge is power.