It’s a good question. One way to look at it is to acknowledge that each individual has a pre-existing motivational profile (whether from genetics, learning or habit, or a combination) that pre-disposes them towards varying levels of motivated behaviour (choosing particular activities, trying hard, persisting for longer, opting out, giving up, etc). This existing level of motivation can be modified, augmented or reduced by environmental factors, such as the influence of family, peers, teachers, coaches, team mates, sport psychologists, etc. You could view this as creating (or destroying) motivation or you could see it as the normal fluctuations along the behavioural spectrum. Either way, I’d suggest that the challenge is to identify ways to encourage behaviours towards the motivated end of the spectrum.