"Long Term investments will always grow.." This has been the psyche that investment advisors advocate to mitigate volatility in investing. How sound is this "fundamental" that motivate investment?

There are no dogmas, beside reducing investing fees to the minimum, diversify and have patience.

Your mentioned sentence has it's truth. But how is 'longterm' defined? Open to subjectivity.

For the Japan stock market and a 10-20 year time window the statement possibly was not appropriate.

On a U.S. and global scale however there was rather steady price appreciation over realistic longterm time windows.​​​

Nothing has changed. Market volatility is normal and should be expected. There will be bull runs as there will be bear runs.

You are having a bias from stories you hear about others losing their retirement funds. But there are more people, who through prudent investing, have made it work. Even during the crash of March 2020.

At 55, your time horizon is a lot longer than you think. It will be an additional 35 years for a conservative estimate based on life expectancy. A portfolio geared at cash or bonds will not allow most people to grow their wealth sufficiently to cover shortfalls over 35 years.

Long term investment will only continue to grow if you choose the right vehicle. This is why most people adopt an equity portfolio and shift towards a 60/40 mix during their retirement years. And often. this is not their only source of funding for retirement. They have a good mix of income-generating assets that pay dividends - both guaranteed and non-guaranteed.

I dwell broadly on investing for beginners here.​​​