Selling SPY Shares or holding?

Im kind of a noob to investing – Im a college student and put in like progressively 9k into SPY over a period of 3-4 years, and in the next 6 months am planning on investing another 20k or so.

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My question is – I have ~20 shares of SPY that I bought @ 450, is it a good idea to

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1. sell them at a loss
2. then short SPY until it reaches the bottom
3. then reinvest in SPY when it reaches bottom

OR

Should I just hold until it goes up past 450 (which may not be for a while)?

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Thanks in advance

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EDIT:

It sounds like people are generally against doing “pseudo-day trader BS”,

What if I were to hold my existing 9k and use the 20k to short SPY over the next few months or is that not a good idea?