An abstract is a part of your research paper, where you have to state succinctly the point or argument of your paper. To avoid an aimless outlining in your abstract, you should invest time and effort to pursue a particular strategy.
That’s why it is recommended to write an abstract after one or more drafts have been written in order to understand clearly the main points that you are going to summarize in your abstract. You should be able to state them in 100 words, and then redraft the paper, so that the major point comes through loudly and clearly.
Howard Gardner, Professor of Education in Harvard University, offers to read sequentially the topic sentences that illustrate the thesis of your paper, when it proves difficult to write the abstract.