This advice and prediction were just so spot on ha!
There is no magic formula. If money flows into a coin it goes up, if it flows out it comes down. Follow crypto news and general customs the world practices (such as holidays, weekends) and you might be able to make better trades.
Buy when stuff is going down sell when it is going back up..

If you're looking for a perfect time to invest is you're going to buy coins on holiday season like what happened recently, last December was the hardest time for investors as most major coins are dropping together with Bitcoin but that's not actually the worst part because it's the perfect time the traders were waiting for, cheap coins are best investments when you know and expect that coin will pump soon.

Whether you chose to invest today or wait for better prices depends on what kind of investor you are. I think there are two types of investors, day traders and hodl-ers. If you are day trading, or at least buying and selling often each week with the intent of making gains based on volatility, its a good idea to watch the price action carefully of your intended investment. Look for market trends based on the time of day or day of week. Honestly, if you have a lot of free time and make it your day job of analyzing markets, perhaps this will work for you.

For those who hodl (hold on for dear life), today is usually a good time to buy. I try not to buy when the coin is on an uptrend as a general rule of thumb (aka up 200% in 24hrs or something). But, it seems like the alt coin market is continually gaining strength week by week. It often seems like there is never a good time to buy. So if you believe in the technology, leadership and purpose of a project then you can reasonably expect the value of their coin to appreciate. Just try not to check the market prices every 2hrs like I do. You may go crazy!

Choose a promising project and invest now. Or buy ETH or BTC. Every week and even every hour the situation changes on cryptomarket. You need to follow.

There is no any kind of perfect time is available for investing because you will never be able to know what will come at future. Only you can know about present situation and can take the experience about the past form of that where you want to invest. Almost all of the coins price is high at this moment than past and no one can predict what will the price at future.

It will increase or be less than present price and it will affect your wallet so that it will depend on the future price. If you can take the responsibility of your future situation then you can invest at this moment and if you want to see and know more about where you will invest then you can wait a while. Time is not the matter but you have to know perfectly about its behavior.

There is only one problem in this scheme - if correction is too deep everyone who waited for it starts to think - is it only correction or the currency squeezed everything it could

There is no optimal time, depending on your own wishes, as long as you find a suitable, potential development, and they have just the funds, you can invest.

Don't wait so long to invest. if you have money to invest and knowing that BTC is growing and increasing its value you have to take a risk to invest and be patient. But you don't need to invest all your money... Try to divide it by savings and investment. We cannot predict the stability of bitcoin, we have to be more aware and knowledgeable in terms of investment.

Just beware even if you'r ready or not, altcoin market still consider as risky activity so if you can't afford to loss, just stop trading.
Although altcoin trading able to generate profit up to 2000% , even experience bitcoin trader will experience major loss too !

I think this time we have to wait the ETH price down to buy. Now the trend of market is too high