Identify The Problem
Remember that every child is motivated but not necessarily to everything or towards what he is seemingly demotivated. It might be the case that he is enthusiastic about sports but he has been exogenously forced to stay at home and not indulge in sports. Identifying the fields that interests him is the first step at getting him motivated. Once you have done that try giving him more time with the things that he likes doing. This will not only improve his emotional state but also make him less grudging about doing the other things that previously demotivated him.
Never Give In
Many parents make the mistake of giving in and succumbing to a demotivated child. If your kid is not willing to do his homework, doing it for him might get good results now, but it will have devastating effects in the long run. He will not only accept the state of demotivation but also revel in it as he will find that there are other people to do the work he is supposed to. This will give rise to a lax attitude and in extreme cases might lead him to fake problems just because he wants to avoid doing something. Be supportive towards his problems but also be firm on the fact that he gets it done himself.
A demotivated child usually suffers from fear of disapproval or lack of confidence. Shouting, physical abusing or punishing him won’t help the situation. It will just worsen it further by pushing him to a deeper cocoon where he feels more afraid and thus demotivated. Every child looks towards his parents for critical support during bad situations. Trying to talk to him about the problem and deciding on solutions is necessary rather than beating him up for the mistakes. But at the same time you should ensure that you are not being lenient to the extent of him taking you for granted. Try to strike a middle path where you are firm and supportive at the same time.
A demotivated child will face a lot of hindrances in the social and academic aspects of his life. While no parents like to watch their child suffer, sometimes you need to. Be courageous enough to let him face the natural consequences of his wrongs. This will teach him the wrongs of his ways and help him emerge a better person. But keep in mind that this is not taken to the extent of being negligent towards him. Try to help him through the problem by suggesting solutions and giving tips.
A demotivated child is not necessarily a failure or a lazy person. You just need to have the patience for him to find his own interesting things and keep supporting him till then. Once there, just sit back and witness the amazing results he deliver.