No matter what your involvement is in music, marketing needs to be a way of life. This is true more for the musician seeking to make a living in music but it generally applies to anyone with goals other than pure aesthetics.
What is marketing? Marketing is the entire range of activities that involve increasing your exposure in the market that you have chosen. It includes but is not limited to advertising, promotion, public relations, product creation, merchandising, endorsements, establishing contacts etc.
A typical musician runs hot and cold in this regard. He or she gets enthused about marketing and works very hard ... for a couple of weeks. Then, nothing for months.
What you need to do is to set aside time every day for something ... anything ... that would promote you and your work. It's a good idea to follow some simple advice from the exercise world and the diet world. Do what you can maintain. In other words, it's a lifestyle more than an emergency event.
The more you do, the more you will develop an attitude, a momentum. Soon, the process will be natural. It becomes something that you don't even have to think about, to do.
When this happens and continues to happen, you're on your way!