Historically, the stock market has gone up. There are tons of times where stocks have been very high.
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When I first started investing, I felt the same way. Stocks were relatively high and I felt very bearish. Nevertheless, I invested the money and to my surprise the market went up for the next year.
Here's the way I like to think about it: I would rather invest money and have the market go down than not invest money and have the market go up. If I lose money when the market declines, at least prices will be lower when I continue investing. If you're a net saver (you are), it's actually a good thing for prices to go down. Pretend you only have 5% of your lifetime investment invested now. That's probably optimistic. If that 5% of your total lifetime investment goes down by 25%, it's actually +EV because you get to buy 95% of your investments at a 25% discount (from the initial price). Warren Buffet once said that he thinks of stocks like toothpaste; when prices go down, the store is having a sale. Analogously, you may have bought 1 tube. If the store has a sale, sure it sucks that you didn't wait until the sale to buy the tube, but now you can buy the rest of your lifetime's supply of toothpaste on sale.
It's much worse, in my opinion, to stay out of the market and see it go up because there will never be a way to recoup those missed gains.