I can sympathize on both points.

I invade a lot, though I have only lately really started optimizing my builds (e.g., prisoner's chain for low-level invasions). Now that I have started optimizing, I find myself getting a bit lazy with hosts that are wearing early-level gear and rely entirely on R1 spam. This leads to me not respecting R1 spam. That is a serious problem, because R1 spam can get you in a heap of trouble if you don't watch your spacing. So, I have had some losses that I could not believe I allowed to happen. And they happened because I did not respect the host. This is not doing either of us any favors, so I hope to break out of this habit.

Also, and this has similarly happened alongside my invader optimization, if a host is clearly new or not optimized for PvP (this is usually obvious), but we have a great fight, I will sometimes get them down to their last estus, leave an ember, and black crystal out. I am particularly prone to doing this when they are a long way through the level and might lose a lot of souls if I kill them.

A bit off-topic, but another thing I have just started doing is sending messages to the hosts and phantoms if we have a great fight, or to a solo host if there was something interesting about the match. The results have been a bit mixed. I messaged a solo host who just destroyed me with the Exile Greatsword in Undead Settlement, down in the area where you hop in the cage to join the Moundmakers. I told him nice job and commented about the reach of the third swing on that weapon. He called me a prick and lambasted me for healing while he was trying to join a covenant. Oh well.

On a more positive note, I sent messages to a couple groups of hosts/phantoms that I beat in a 1v2 and 1v3, just thanking them for a great fight and that it was a lot of fun. Somewhat to my surprise, I got entirely positive messages back from them. I actually ended up re-invading the host and phantom from the 1v2 just a few minutes later. I dropped them some embers and black crystaled out. And then invaded some other people. So much fun.