I want to refuse the next contract of the offer for long term work

[mayu_shikaku]

I have a question about contract.

I have a contract of fixed-price projects.
This job's offer is for long term work, but the contract is only for the first some files.
We agreed and I promised how many files I would complete at least per a week,but we didn't negotiate how long we would have worked. 
I have finished the task of some files and he paid all milestones.Then he has required me to keep working.
But I don't would like to keep working this job because there were some troubles and I can't trust him.In addition,the task was demanding than I imagined.I have negotiated again but it hasn't been going well.

I would like to ask that
1.It is only on chat and doesn't be contracted that we works for a long term.
2.The contract has completed perfectly and he paid all milestones.I can end this contract.

In this case,is it a violation to refuse the next contract?

[ladyelexia]

You never have to keep working when you no longer want to do so. Simply tell your client in a very respectful and polite manner that you have enjoyed working for him/her, but that at this time your schedule/workload/life will prevent you from continuing at this time. Thank him for your past experience and make sure to be positive in your tone. This will ensure he/she is not offended and thus leave a reactionary bad review, and it will end further conversation about more work that you are not interested in.