Living on assumption and promises is more like spending money you haven't received. People can make promises but how sure are you that the promise will be fulfilled.
I will give you #5000 on Monday, how sure are you that the money will come in on Monday? Promises and assumption has caused alot of people there job, imagine leaving your recent job because a friend promise to get you a better job. This may even cause someone his/her life if one base most of his/her lifestyle on promises and assumption.
I could remember when one of my friend put himself into serious debt believing he has already won a huge money from gambling. This was some year ago, match between Besiktas and Benfica. It was the last game of my friend's ticket. After 3 goal ahead by Benfica in the first half, he believed the game was over and Befica has won. He called us to celebrate. We started drinking and eating at a bar to celebrate this. After the end of the game, we were shocked as the game ended up in draw with 3- 3. This landed my friend into serious debt that took him some weeks to pay.
Similar stuff happened to me when I spend my finance school fee believing my salary will be paid in two days time but was shocked after the salary was prosponed due to some reasons. The school fee was needed urgently and this put me into serious issues but thanks to my friends who bailed me out. This same issue has happened to us once or twice in our journey of life.
Economically, this can affect our business. I have #300,000 to start a business. My Uncle promise to give me #200,000 to add to the business. Therefore,I made a plan of #500,000 for the biz. It was an agro business (livestock farming- piggery) so I start the business with my own capital. I acquire a portion of land and make some structures with all the #300,000 I have believing I will stock the farm with livestock with the money my Uncle promise me. This was a serious shock when my Uncle come up with stories and couldn't fulfill his promise. This render my plans useless. Remember I could have start the business with the #300,000 I have alone although in a smaller form. I have to get loan to balance up with this. If not for the loan my plans would have been highly be affected.
It's better for one to learn how to plan on money at hand and not on promises and assumption.
The first example where your friend placed a bet is quite a common feeling for anyone who has been investing in companies a while or engaged in games like playing poker. There are situations that make it feel like you've already secured a win, but celebrating too early will lead to great heartbreak. There's an example in the gambling section of someone who placed a million dollar bet at 1.01 (odds the represent the player is extremely likely to win) and who ended up losing, so it could be a lot worse. The real moral is that even sure fire predictions can lead to major upsets, at least if you're doing something like buying shares in companies you have many opportunities to cash out on the way down, whereas gambling tends to be completely binary (you either win or lose immediately at the outcome).