Everyone needs the motivation to undertake any task. This motivation can be an intrinsic one (doing something for the sake of it), or it can be an extrinsic one (doing something for external rewards). Whatever be the source of motivation, everyone will agree that people need it to get things done.
We need motivation not just for starting up of some project but also for continuing with it till we reach the end goal. This makes it essential for us to have a continuous source of motivation which can help us keep up the pace. When we start losing interest, this source can provide us with a short burst of motivation to get going.
For most people, it is often easier to get the motivation required to start the project than required for continuing it. Even if the latter might be lower in magnitude. This is the reason many of our projects are left hanging in the middle, and we wish to complete it someday. This can be as small as not being able to finish reading the book which we started.
So the source of motivation which can provide us with necessary motivation shots should also be resistant to our inner state because if our internal state were so helpful, we would not have lost interest in the first place.
One method to develop this type of source is to have a healthy competition with someone close to you and who has also undertaken a similar project. This person can be a friend, colleague, acquaintance etc.
The critical point here is that the purpose of this competition is not to beat the other person and get ahead of them. Instead, it is to see their work as a source of inspiration and to benchmark our progress to someone whose capabilities and skills we are aware of. This will give us an idea of what we are capable of achieving, and we will try to reach that level. Imagine you and your friend reading books and sharing the progress and learnings with each other.
This whole process will also work for the other person and will create a virtuous cycle where each person is a source of motivation for the other. Both the person will try to reach the level of other or become slightly better. This recurring gap in the progress level will serve as a mini-challenge which can be easily achieved with the existing skillset and thus will serve as a source of motivation rather than discouragement.