This is infact a luxury if you can trade the London session because most of the move start in London session and you get the best entries in start of London session. The liquidity and volume adds up at New york open and that is the time to take profits and close your trades running in profits.
I know that the best time to trade is when two markets like London and new york are open at the same time, for more information about this you should consult a forex calendar, because i don't know your time zone.
I believe that the time for trading is individual for each trader. Everything depends directly on your trading strategy and your daily schedule. The main thing is that you are not sleepy and cheerful, it is very important that you make cold decisions and external factors do not disturb you.