It's mostly like my own fault, in different ways. 

Projects need to be correlated in size to the amount of resources that are available to create and ship them. 

In addition to that, you've got a learning curve about the proficiency in the timeframe when the project is done. 

You've also got marketing concerns to think about -- who is the project for, and how do you access those people? 

Is the project created for a group of people who don't exist? 

Is the project created for a group of people who don't need it, or don't have money? 

What is the value you are creating with the project, and how can the value be extracted further in the future, so that you can sustain growth? 

.:. 

There have been multiple mistakes I've made: 

One project I didn't do any outreach whatsoever, just to see what would happen, and the project failed. 

Another project failure of mine, which was a really common one for me, is me thinking "This would be cool, because I like this and therefore people will give me money for it, because I have excellent taste." 

-- Wrong. 

People think that they have excellent taste, and so you've got to sell to them based on what they are already excited about, and even then, you've got to drill down and be specific about what you're sharing with them. 

I gave everything away for free for the first year - that was a mistake. There's no tension there. 

I didn't keep careful enough accounting for the cash flow needed to provide prints and stickers, at one point, which resulted in a lag between fulfillment and orders, which gave me a bad reputation for a brief period of time [in my mind?] for not being someone who fulfills projects or ships products quickly. 

I promised too big, and then wasn't able to deliver on that promise because I didn't promise in accordance with the funding that was available to me to execute the project -- I've since learned to let the audience carry an equal portion of that weight -- "If we get X funding, I can provide us with X results." 

I imagined that my tastes and ideas of a good time were the same as other people's tastes and ideas for a good time -- offering them to pay me to be models in my work, not really understanding that people want to pay me to paint other people who are more exhibitionistic to be models, so they can be voyeurs, via the art medium. 

Also, Projects were too small, or too big. 

And then there were some competency errors: 

Like, I didn't tell a good enough story. 
Or, the art wasn't up to par. 
Or, I didn't obey certain conventions of comic presentation / panel structure. 
Or, I wasn't sexually explicit enough,
Or, I didn't do a clean enough job on the text. 
Or, I didn't proofread. 

Beyond that there are just stylistic choices. 

Like I really enjoy doing impressionistic, mildly chaotic, pallette knife type paintings, and more bubble soft and shiny, dripping hentai is more popular. 

And I chose to do some indie original content stuff, when I should have done fan art, or public domain IP work. 

.:. 

All of these areas sort of need to be examined and good choices need to be made -- and you really only have one shot per experiment to make something happen. 

So it's like "If I do this, what happens?"

And then I need to try and run through the obstacle course of making the project in a way that is financially viable, so I can do it again, with greater profitability. 

It's really a challenge. 

This is why smaller projects are good for project based artists who are just starting out, because it allows for more rapid learning / iteration. 

But even that has its own sort of drawbacks, because larger projects are more profitable and therefore more sustainable. 

But in order to execute larger projects, you need to have larger funding security, and | or more minimalistic / leaner operating budget.