A gain is a gain! Downside to short term gains?

I was thinking tonight. Ok, my job pays me and they take out taxes. So whats the downside to short term gains, especially in a volatile market?

I mean if I make an extra $100 why not just quickly cash it out and pay a bill with it or something?

Then at the end of the year I'll pay my short term tax which is the same as my current tax rate anyways?

And I'll still have MORE money in the end to pay a bill with or whatever.

Especially in these nutty times when the market may crash 50% and not recover till after I'm dead in 20 years or something!

Its like having another part time job!

As long as I don't make enough to throw me into another bracket which I'm sure I won't anyways!

So I don't see short term gains as necessarily a bad thing other than paying taxes.

I'm still left with a gain! And a gain is a gain! Hey I wouldn't pass up a $100 bill laying on the ground!