Yeah I have had such experience even if not directly and not necessarily on improvement. Some kids in the family have friendly "bet" with their siblings to forfeit some portion of their food to the winner. Like while growing up, some children bet on the return of either of their parents who had travelled on a particular day. They do such bet because they are missing that parent and so they are in expectation of the return. Another kind of bet like that is probably in video games like play station, some friends do bet on the best player and winner.


To stop myself of a habit not worth it. Like for example during the end of the year, many smokers bet on themselves to stop smoking but whether they go back to it is another discourse. 


I know weight lifters also bet on the amount of weight they can lift. However, I may bet on myself to be able to achieve something or improve myself like reading a particular book or doing a particular thing that have been difficult to do but it is not monitory bet