The principles involved are absolutely right. When price is in a consistent uptrend, you should be long, and when there isn't as trend, you should be in cash. This is the foundation: the shorter-term stuff is optional / cosmetic.
My opinion ...
It starts with understanding what wealth is (friends, family, peace of mind, possessions, being out in the sunshine ...)
Next taking a position in forex, because every equity, commodity, and bond market is priced in a currency, forex is the ocean upon which everything else exists. Everyone has a forex position, even if it's just "cash in the bank" (i.e. their local currency in a banking institution in the country where they reside)
Next determining your own attention span, how often you are able to sit and make decisions about what positions you are going to take, etc, because that drives the time window that your positions and trades should be. Obviously you aren't going to want to scalp if you're only looking at the markets once a week.
Next develop some kind of basic long term positions, where you want to be when you essentially aren't paying attention to what is going on, do you want to be holding some kind of cash, short term treasuries, longer term treasuries or corporate bonds, cd's ...
Next figure out the tax implications of everything you're doing ...
In my opinion those kinds of things are foundational, before you even move on to ...
NEXT ... you can start focusing in on shorter periods of time. The shorter the period of time, the more attention your trades and positions require, and the more potential there is for both gain and loss, especially when employing leverage. Do you have the attention span and time to sit down once a week and change positions, once a day, once an hour, once a minute, to automate to trade by the second, millisecond, nanosecond ? The shorter the period of time, the more trading is going to be a "job".
Edit, and if you don't have some kind of feedback mechanism to determine whether you are making things better or worse by trading shorter periods of time, then that's a problem. If day trading for a year leaves you worse off than if you had just bought a 1 year treasury, what's the point ?
I think it's very responsible for the poster above to back off from short time frames and focus more on the underlying positions s/he is taking. Everyone should probably do that from time to time to gain perspective, take a vacation, etc.