One way to earn more money as a freelance writer is to write more per day. You can set a goal for a number of words or a number of articles per day. Depending on what you charge, you can create an estimate of how much money you can earn by writing a certain amount each day, and do your best to meet or exceed that income goal. After I get used to writing a certain amount per day, I increase this goal so that I can allow for growth and an increase in income.
It takes discipline. As much as I love writing, every once in a while, there is something else that I would rather spend time doing. I am usually distracted by people: I am a people person and I love to joke around and have fun. I have to sacrifice some time with friends and family to focus on my work, and that is challenging sometimes. Acknowledge what your major distractions are and make an effort to put those things aside for your goal.
Sometimes you just need to start. If I find that I am lacking motivation on a particular day, I try to just start writing. Once I start coming up with ideas I start to enjoy what I am doing and I keep writing from there. I forget all of the other things I could be doing just by the action of opening up the Word file and putting some thoughts down.
Take an occasional break. Break up your daily writing goal into thirds. After each third is done, take a break. Get up and stretch, eat something, Tweet, update your Facebook status, or whatever you like to do. Remember that you are still on working time, so keep the breaks short. Fifteen to thirty minutes is usually enough for me to refresh my mind enough to sit down for another writing session.