Try to enter when the price comes to you, and not the other way around.
This is surely the underlying "key concept".
It's also an issue on which I know many traders have found huge assistance from reading books. From my own limited knowledge of the subject, I'd suggest anything by Dr. Brett Steenbarger who's a very successful trader as well as a very successful psychologist (and perhaps especially The Daily Trading Coach: 101 Lessons for Becoming Your Own Trading Psychologist, and/or A Trader's Guide to Self-Discipline: Proven Techniques to Improve Trading Profits).
And for what it's worth, I'd recommend avoiding anything by Mark Douglas - a self-admitted "failed trader" - (and perhaps especially Trading In The Zone, which I made the mistake of reading and firmly think is overinflated, ultra-repetitive, dreadful nonsense).
Edited to add: Zen in the Markets - Confessions of a Samurai Trader, by Edward Allen Toppel, is also interesting, as well as "light and short".
Hope it helps.
