I was thinking about human nature and it seems quite natural to also utilize the negative as motivation. Some examples:
In sports it is not only common to cheer for the favorite team to win, it is also quite common to focus on being against the other team. It is very possible that the other team is full of talented, intelligent players, but just because they are against your team, they become incompetent, idiots. The noble way might be to wish both teams to play their best and let fate decide. My experience is people tend to get more motivation from wanting their team to do it's best and destroy the other side.
Politics is an area that I find completely humorous. I can't understand how we all keep falling for the same tricks year after year. Every election I have ever seen, politicians try and give the impress they they are nice, honest people and would never say a bad thing even about the devil. Unfortunately, because of some circumstance, or often because they profess that their opponent started first, they are required to use negative press. Just saying the good things about themselves never seems to be enough, they must also point out the negative things about their opponent.
These examples get me thinking that the negative side, or what I call push, is also a powerful motivator to action. Of course, focusing on the positive is great, and a little bit focusing on the negative can also be helpful.
To take this a little bit further, I believe that if there is no external enemy, then people will create an internal enemy. What does this mean?
Think about countries. If a country is experiencing a period of relative peace and security, there will still be troubles and disagreements that come up. If there is no external enemy to blame for these issues, then people will start looking inside the country. The North and South will blame each other. The urban and rural population will blame each other. One way to unite these people is for a real or imagined external enemy to show up. For example, if people can be convinced that it is some external force that is causing their problems, then they can be united against this new enemy.
When looking to accomplish your goals, maybe try and come up with some external enemy that you are fighting against to achieve your goals. If you are trying to earn money, you could use something real like time and inflation that are stealing your money, or even make up something like some little green monster that is taking all your money. If you are learning to be positive, then you can imagine the failure you will face as a result of the negative energy you express.
I don't have a fully formed theory on using negative energy to your advantage, I just propose this as a theory that if we completely ignore something it can grow out of control, so spend at least a little time to be aware of it and don't expect it to disappear. Negative emotions and motives will always be around, so at best we can try and use them to our advantage.