People with simian lines know how to get what they want, and when they know what that is will stop at nothing to get it, and have such a strong driving source. However, if the want isn't there, the drive is nil. They can also get quite moody, especially when their needs aren't met.
Basically, the simian line is often a gift. People who have them really have this extra helpful connection between their heart and mind that makes them able to accomplish a lot. Whether used to create new helpful inventions, or become a serial killer, a lot of power comes with it.
Although this is just an overview, to really know how yours personally effects you, a lot more needs to be considered. Once again, whether or not it's a pure line, as well as if it is on both hands, what type of hand you have, what other lines will change it's effect, it really is much, much more complicated. But basically, it doesn't make you a failure, it isn't necessarily bad, but like everything it can be.