Be sure about what you want and when you do decide please don't doubt yourself. Remember that you're sending a request to the Universe which is created by thoughts and therefore responds to thoughts. Know exactly what it is that you want. If you're not clear/sure, the Universe will get an unclear frequency and will send you unwanted results. So be sure it is something you have strong enthusiasm for.
But the one who really first articulated the Law as general principle was Prentice Mulford. Mulford, a pivotal figure in the development of New Thought thinking, discusses the Law of Attraction at length in, for example, his essay "The Law of Success", published 1886-1887. In this, Mulford was followed by other New Thought authors, such as Henry Wood (starting with his God’s Image in Man, 1892), and Ralph Waldo Trine (starting with his first book, What All the World's A-Seeking, 1896). For these authors, the Law of Attraction is concerned not only about health but every aspect of life.
Your thoughts and actions create a result. Everything you think, say, and do will have an effect. Every action generates a force of energy that returns to it in kind and that energy continues to flow back and forth. If you don’t have a clear understanding that this is how things are, then the Law of Attraction makes your reality seem like the world is bleak because you don’t understand how you are attracting the very thing you wish to get away from. You just do your best to keep thinking happy thoughts in the hopes that something good will eventually occur.