There is an old legal term that goes along the lines of "The artisan promises the skill of his art". This of course means that the electrician or builder that you hire is expected to do a good job. This is taken for granted. I like to think that artists do not have to feel the pressure of regular artisans, but is this valid?
A collector does not have to purchase a painting. This is a can be a relief for artists as it means that there are no strings attached. You like or leave it - simple. However if sales means rental paid then there is pressure to sell. The message is clear then. If an artist wants to sell art then the art must be of a high standard. It is the implied promise.
Now I know that if a collector has no interest in beach scenes and wants a still life or an abstract work then no amount of quality will make a sale. Those issues aside what is most important for the artist in the long run?
To my mind a good chance of consistent success professionally means regular and disciplined work. Not very romantic is it? On the bright side if art is your passion then it is not much like drudgery at all. Sounds like bliss to me! Consistent, but varied work will result is much quicker progress. For example if I paint the same subject then each version must be sufficiently different to keep my interest. Also I do not like to paint in the studio every day. If I can vary the routine by painting outdoors or doing something else like preparing painting panels or framing then I can refresh my energy for painting the next day. On other occasions reading up on master artists, sketching or simply observing the clouds go by all become part of a process that is art. This is part of what collectors should expect and receive from the professional artist.
There is no substitute for trial and error over time. Yes putting in the hours will speed up the learning, but it still takes time. To this must be added the ability to take risks and make mistakes. Sometimes embarassing mistakes! But no one gets hurt - maybe a bruised ego, but we must move on quickly and learn from the experience. I find that many creative folk avoid painting due to fear of making a fools of themselves. Sometimes they fret over the cost of materials wasted on failed paintings. What a shame. Perhaps it is for the best, because making mistakes and absorbing the costs are part of the deal.
Part of the artist's promise is not to compromise on quality of materials, framing, packaging and all the other bits and pieces that go with the business. But first and foremost is having a work ethic filled with the joy of creating art. From this all else grows and it will be good. The artist's promise is fulfilled.