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.