It is truly hard for me to give a certain answer what does success exactly come from. I believe that it is a wrong way to depend only on chance or risk. On the other hand, I am not so sure that careful planning is the only factor for success.
When we talk about success we should be aware that it has different measurements. I can be a successful person in my job field, for example. It may mean both I have planned carefully my way to success and I have taken my chances right on time. If we quit our job looking for a better paid or more progressive work position, the real situation at work can destroy at once our expectations if we do not have enough information about the job, we apply for. That is why, any important decision that refers to our success at work should be made after careful planning along with taking rational risk.
Another aspect of success, I believe, is making and keeping a happy, well-bound family. In this case some people would say that it is crucial for everyone to know his partner very well before a serious engagement. While others feel that meeting the right partner is a stroke of luck and only a week appears to be quite enough for them to find themselves at the altar. Referring to love and family success results sometimes neither from taking risks nor from careful planning.
I hardly know a person who does not want to succeed in life. In my opinion, both viewpoints in the topic are extreme answers to the question: `which way we should chose to success`. Life shows that everything in Nature should be balanced so if we find the same way sooner or later we will see that real success comes from taking risks and chances after careful planning.