We can strengthen the will by exercising it. One simple practice is to delay gratification, for example instead of rushing at the favourite food, go slow and delay it. Or else if an impulse or passion or a surge of desire moves us we should step back and instead of immediately acting upon it, look at the possible consequences, consider whether it is the right time and circumstance, see whether it is going to help us move towards the goal we have chosen or is going to create complications. In short never to rush into action or act without reflection. One should practice stepping back before action and see the transient nature of our satisfactions, to offer all actions to the Divine before undertaking it, to make a workable routine and be regular and punctual in following it. To slowly increase the level of challenge to the will. Most importantly pray and ask the Divine to give us a strong will. These are some of the ways to strengthen the will.
Affectionately,
Alok Da