Is it bad that I have forgotten how to do algebra

I used to be brilliant at it.

Maybe you are occupied in your mind by singles & dating, which is a totally different subject.
It is not bad, unless you really need it for your job.
There is more in life than algebra, like dating ...

It may mean that your brain is deteriorating, or that you have brain problems, so if that's the case then yes, it's very bad.
However, if it has bean many years since you have done it and you simply don't remember due to extensive time, try taking a refresher course. If you find that you start to remember how to do it, then it is not bad.

The source at a quick glance looks good, I recently found it and so far have had no problems.

It is not a mathematical question to ask "is it bad" because the property "bad" is not mathematically defined.

In a mathematical sense, it is not bad or good to forget how to do algebra.

The only numbers that are really essential are 0 and 1, and all other things can develop from there.

Yes.

Relearn it at www.khanacademy.org

If you don't use it enough to remember it, you lose it.

Could be a case of "use it or lose it."