A common guide to trailing a stop is to start trailing it when the unrealised profit reaches the same amount as your initial risk that would have been lost if your stop-loss had been hit. so imagine you have a stop-loss of -£100: as soon as your position reaches +£100, your trail your stop to your entry price, then move it every time price advances so that your stop is always £100 behind the current price.
This is OK, but the TA which decided your initial stop-loss should be X pips behind your entry is now long gone and not relevant. So a trailing stop at a fixed amount like this will always incur the maximum risk which is maybe not necessary. so you could also use new TA features like support or resistance as they appear to set your trailing stop - as long as these are never more than -£100 max.
A trailing stop means you will never lose big but you will almost certainly never win big through running a winner on a long-term trend or pyramiding your winning positions.