There can be many different conclusions to the same research paper (just as there can be many introductions), depending on who your readers are and where you want to direct them (follow-up you expect of them after they finish your paper). Therefore, restating your thesis and summarizing the main points of your body should not be all that your conclusion does. In fact, most weak conclusions are merely restatements of the thesis and summaries of the body without guiding the reader toward thinking about the implications of the thesis. Just as a conclusion should not be just a restatement of your thesis and summary of your body, it also should not be an entirely new topic, a door opened that you barely lead your reader through and leave them there lost. Just as in finding your topic and in forming your thesis, the safe and sane rule in writing a conclusion is: neither too little nor too much.