NCIS I think you are too hard on yourself, your dog has always been very well behaved, you just have extremely high standards.
In our case, Lurcherboy only has one fault really - that he has suffered from Isolation Distress since we lost his companion last year. He's such a good lad other than that, but him having ID causes me problems because I need to take my other dog out individually to work on his issues, but I can't leave Lurcherboy without him or he howls. Other than that he is the gentlist, sweetest boy, well behaved with decent basic training - although bless him, he's not the brightest so I haven't trained him any further than that.
Pip has a lot of issues, stemming from both a bad start, right from birth, before he came to us and then illness resulting in him missing a large chunk of his socialisation. Obedience-wise he's pretty good, decent recall (whistle trained) - especially for a Lurcher and has all the basics down pat, plus a few tricks on the side. He's good with people of all ages, including children and is no trouble around the house at all. Unfortunately despite being able to carry him out and about for socialisation, so he's fine with just about everything and everyone, he wasn't able to mix with other dogs until he was 17 weeks old and then had two bad experiences in a row where he was rolled by dogs whose owners were nowhere in sight.
He's now extremely fearful of other dogs. We've worked hard on it and seen two behaviourists, but they both told me we're doing everything right, it's just going to take a lot of time and effort and he will probably never get to the point where he's completely happy around other dogs. 
His other fault is Separation Anxiety, again stemming from his difficult start. He can't even be left just with Lurcherboy, as he gets very distressed and screams the place down. He's come a long way. I didn't used to be able to even step away from his crate for a second when he was younger, then for months I couldn't leave the room, let alone the house, so couldn't even go upstairs for a second without him yelling. Now he's fine with me in and out and up and downstairs and even doing stuff on the drive or in the front garden and can go a maximum of an hour (realistically he's more comfortable with around 3/4 of an hour) at home without me. It's slow progress, but we're getting there.
As for what other dogs could do so their dogs don't negatively affect mine - the age old thing about not letting their dogs run up to dogs that are being kept on lead. I accept that sometimes it's just an unfortunate set of circumstances or a generally well behaved dog that suddenly goes deaf and decides not to recall. It's the owners who walk around the park staring at their phones, ignoring their dogs and letting them run up to anyone and everyone that drive me scatty - as do people who open the boot of the car and let their dogs run while they either wait by the car or saunter slowly around, so they're often on the opposite side of the park to their own dog and either can't see or ignore whatever it's doing.