I track a number of stats on all my trades. One of these stats is how many R the trade could have made if I had let it run and taken profits at the absolute best spot. This is called the maximum favorable excursion (MFE). By tracking your trades in this way, you will gain insight into what areas are reasonable to take profits. If you see that only 10% of your trades make it to 4R, you may want to partial much sooner and take bigger chunks with those partials.
A lot of this is psychological as well. I keep very tight stop losses, and I am quick to jump out of a trade as soon as it doesn't work. I settle for small gains on my trades, but my win % is very high. This contributes to a decent profit factor, which is ultimately the most important aspect of your trading. I leave a lot of money on the table because I exit quickly, but I don't like to sit through pullbacks or give back unrealized gains. I'm happier this way, and that's important.
You will need to do this type of work and self reflection to figure out what your trading is capable of, and what your psychology will allow.