Most electrical work is not difficult. If you shut off the power and test to be sure it is off, you are safe from shock. It doesn't take a lot of time or effort to avoid a shock -- just a little care and a few simple steps. Learn these steps, then make them habits.
Pretend it's live
Professional electricians have this simple rule: Even after shutting off power, always act as if the wires are live. That way if someone accidentally turns on the power or a tester gives the wrong reading, you're still protected.
Pretending each wire is live means you should never touch two wires at once. Nor should you touch a wire and a ground at the same time. It is good practice to touch the bare end of a wire only with an insulated tool, not your fingers. As an added precaution, lightly twist a wire nut onto the bare end of any wire that you are not working on -- good assurance that it will cause no harm.
Get into the habit of taking the time and trouble to provide yourself with double -- even triple -- protection. In addition to shutting off power and testing to make sure power is off, wear rubber-sole shoes and use tools with rubber grips specifically designed for electrical work.
A single lapse of concentration can create a dangerous situation. Eliminate all possible distractions. Keep nonworkers (especially children) away from the work site. Don't listen to the radio or a music player while you work. Check and recheck your connections before restoring power.
Give yourself plenty of time to finish a job. If you need to leave a job and pick it up again the next day, start at the first step: Make sure the circuit is shut off and test for power before proceeding.