angelnish - this is the best question in trading and the hardest to answer. I can tell you my current thinking, still developing, don't regard this as the only right answer.
(Please note I am a swing trader and find my average holding period is 3 sessions, including the entry and exit sessions. this applies whether the trade is closed automatically or manually and whether it closes for a profit or a loss.)
Day 1 - Set profit target for half position at r:r = 1:1. so for every £1 I am risking on a position I will bank 50p if price goes into the black. The remainder has a trailing stop.
Day 2 - Close remainder of position as session ends if 1:1.5 or better.
Day 3 - Close remainder of position at 1:1 or better or in any case as session ends.
You will see I am not trying to wring the last £ from any position like the books tell us, I am trying to bank profit early before it goes back into the market (while I was temporarily right) and get out of the market to release resources for the next trade. Maximising r:r is for me at least a vain ambition: I might be right temporarily, but I just can't stay right for long enough to get a 10-bagger.
It's possible this approach will only make sense in markets with a closed period each 24hrs. Please note also I can't screen-watch continuously but have to dip in at midday and in London's last haf-hour.