If you are working for a single client and have such micro management that your work is subdivided into tiny tasks and feel that rejecting it would be an issue,

If you are working for a single client and have such micro management that your work is subdivided into tiny tasks and feel that rejecting it would be an issue, then you are not really self employed, you are a remote worker... Normally the typical advice when someone who is self employed has too much work is for them to raise their rates, but this works much better if you have more than one client since that does mean that you still have some clients to fall back on otherwise... For your specific situation, I'm not sure what to say, apart from advising you to try to get out of this situation by 1) finding other better paying clients and 2) slowly reducing the tasks you do for your current client to the more value added tasks.