Will is not desire. Will is not doing what you are interested in. Will is the ability to decide on what you put your attention and keeping it there. You need presence and energy for that, but above all you need the belief that it can be done in the first place. Faith in the divine power that is consciousness.
Will can be practiced and developed. Fortunately you don't need Will to develop Will. You just need to become deeply interested in Will. Also you need to set goals. Otherwise you would not know where to put attention. Will implies having goals. Having purpose. You cannot have Will without purpose. That is why setting goals and making todo lists etc. is so important to practice Will. Everything is determined by Will. Success, happiness, health and so on. Will is an aspect of consciousness. The creative or outgoing aspect. It is interesting to see that creating is tantamount to focusing of consciousness. To create you just need to direct.