I appreciate that it sounds like you had a bad experience with a client though.
That helps. What helps even more is to have a nice fat savings account that allows you to negotiate properly, to weather the inevitable dry spells, to build a solid base of clients that value you and that will repeatedly hire you.
> take some insurances
Against what? 90%+ of the freelancers are not even insured against loss of income from health related issues. The remainder is well off enough that they can probably afford to take the risk.
> whether you have 1 or 3 clients at one point in time is immaterial as long as it doesn't sour your relationship with your clients
Until: that one client goes bust, there is a 'policy change', the project/product you are working on gets axed, the economy burps, your main contact at the company gets fired and the new guy or girl doesn't like you and so on.
> I appreciate that it sounds like you had a bad experience with a client though.
I appreciate that it sounds like you haven't had a bad experience yet, but that makes you simply less experienced. Give it some time and you'll see all of the above and variations on those themes.
Here is a 2011 booklet I wrote on the subject.
in my jurisdiction there are for example some excellent guaranteed income insurances covering various situations. they won't pay forever, but they'll pay. income replacement due to health issues is covered by normal social welfare in my jurisdiction as well
all of those things you mentioned happen regularly to employees. they are harder to let go, sure, but employers have a lot more leeway to make your job hellish enough to force a resignation, or if the economy is really bad overall they can throw their hands up and say we're cutting divisions of the business with no objections from the law in most places. sure you can go to your work council (hope they are on your side) about it, or to the union (hope they have time for you and you're lucky enough to have enough evidence to win the tribunal) or the lawyer (hope you have a legal assistance insurance and are ready for years of process and fees). employees without a savings buffer are similarly vulnerable in these circumstances
the biggest reason to stay an employee if you can consult instead where I am is really the unemployment benefits you can get, but that now takes up to 10 months to actually start paying out due to how understaffed the government is. so again, best have some reserves. the next biggest reason is you hate paperwork