I notice that with age, it becomes easy to lose motivation for starting new projects or even continuing to work on something that I have been doing for a long time. Inspiring stories of people who start something relatively late in life and through consistency and perseverance achieve results that are beyond average in that field, even for much younger people, work very well for me in such periods of uncertainty.
There are many inspiring life stories that can be found in books. For example, I have just heard an interview with Jack Canfield, who specializes in putting together collections of such stories.
In my own experience, one of the most influential encounters was the one with a Japanese lady, about sixty years of age, who visited our kendo dojo several years ago as part of the delegation of rather high-level kendoka. After the practice, she asked how long I had been practicing kendo. I was then in my early thirties and had started only a couple of years earlier. I thought that it was a hopelessly late age for starting kendo and that I had no realistic chance to ever achieving the level that this lady was at. However, she said the she started practice even later in life, after her children had grown up and left home. Naturally, this made me re-evaluate my entire outlook at kendo practice.
Activities that require certain level of physical fitness are the prime examples, where such inspiring stories are most impressive. I think that in other areas, such as arts, photography, studies, etc. there are even fewer excuses for not starting something new at any age. In fact, I recently read that from a psychological point of view, it is the joy of new experiences, and as a consequence, active seeking of new activities, skills and knowledge, that constitutes the essence of a youthfulness.