What you work out for; Below is a chart showing the difference in the number of reps you do for weightlifting, and what you achieve.
I train for strength, and do a 3×5, so aim for a max of 5 reps on the most weight I can do. Obviously if you are into having big muscles like bodybuilders you want to be doing about 10 reps, and so on.
Today is the day you can take control of things. The first step is always the hardest.