How long can we ignore the fundamentals?

Hi everyone, so I'm pretty new to investing - been about a full year now. For context, I'm 80% in ETF's and about 10% in GOOG. I'll admit, I really don't want to face a downturn with the amount of my life savings I have in the markets, so I tend to get in, make a quick buck and then get out. Ideally I'd like to just buy and forget, but given videos and research I've been doing on the fundamentals of the market, I literally can't get over the feeling that a downturn is around the corner, especially considering the POTUS. I feel it's inevitable that another liberation day is coming and taking that opportunity next time is what I would prefer. Then, you get on reddit and common copy paste cookie cutter advice is, just buy the index fund and forget "don't time the market" etc etc. I tend not to believe this advice. In fact, I believe it's actually not that hard to time the market. We get a 15%-20%+ downturn? Great, I click a button and buy like a damn robot. I don't see what's so difficult about this, no I will not let emotions cloud my judgement when that time comes. I will simply buy at a discount. It's evident to me now that we are in an irrational market that is not driven by fundamentals but rather by...I don't even know, just irrationality I suppose? I'm also seeing that we have basically been in a bull-market for the last decade. So my question is, how long can this continue? Of course nobody has a magic orb, but given your experience (I'm talking to people who have been in the markets way longer than myself), how long can this realistically go on for - and what strategies or tips could you give me if any? Much appreciated.