We cant really just that be careless on investing on the time or moment that the market is on bullish situation or something that we can call it a peak, because on the moment that the market will really be making up some corrections then you would really be that finding yourself get caught in the dump on which it will really be causing up that huge negative into your portfolio. Next? Possible if you cant be able to control your emotion
then you might be ending up on having that panic selling action on which we know that this is really that commonly happening specially into newbie investors.
Right time? If you do go for long term holding then this one wont really be something an issue or something that you would really be minding about but if you are someone whose really that trying out to make money in a short period of time or simply minding about making profits then you should really be that wise on taking up positions in short term durations on which you do really needed up to buy when it dips and sell out when it peaks. Rinse and repeat then you would really be that considered to be that a good trader but of course there's no way for it to be assured.
I agree, if you go long-term, there is no such a big difference on when you do it, but rather when you will end it and for how long you are okay to hold it.
The goals should be clear from the start and remain that way for the investment to be successful.