I have my own reasons why I agree with the statement that successful people try new things and take risks. There are many viewpoints regarding what the main characteristics of successful people are. In my opinion, one of the main reasons for supporting this statement is that successful people can learn important and very valuable points from trying new things. The other reason is that great success requires taking great risks.
For writing an introduction you should start it with a motivator, then add the thesis and finally give your opinion. It is not a good idea to begin the introduction with something about your idea. The opening statement should provides some general information. The thesis introduces the main idea of the essay, and at the end of the introduction you mention your opinion to show that your are going to discuss which facet of the matter.
In sum, I believe that success and trying new things and taking risks go hand in hand and to achieve success you should consider them.
In the case of conclusion you need to reword the topic/thesis first, then write a clincher (ending statement). This is an "agree or disagree" topic, and you already mentioned your opinion in the introduction and you supported your opinion through the body paragraphs. So, you do not need to state your opinion in the conclusion again. For other types of topics you should give your opinion before stating a clincher.
Hope this helps