@ferretface has it, for me.
My own dog is reactive - though these days he is far less so than he used to be.
The biggest single difference was me making a promise to us both that I would do my best to shake off any reactions. It was my frustration and grief afterwards that was adding to his problems, I think. Not that I would ever take them out on him but walking alongside a human that was silent and (sometimes) crying must have been worrying - thereby reinforcing the link between other dogs/humans and bad things happening.
As I started to work on just getting on with the walk as normal after a reaction - or cutting it short if I couldn't manage more, rather than perservering like a martyr - life got easier. He recovered more quickly after a reaction, and so I found it easier to recover more quickly, so he found it easier to and so on. Like a snowball. A good snowball 
It helped me to reframe how I thought about his reactions. He is an extremely smart, loving, sensitive dog who is always doing the very best he can. Sometimes that best is great, sometimes it's not - but it's always his best.
More often, these days, his best suprises even me with how good it is. Earlier today a lady walked right by the car with two dogs - something that always sets him off. He didn't make a peep, just watched them go by. This is unprecedented.
None of that is meant to make you feel bad, OP, or suggest it is your 'fault' in any way. Life with a reactive dog can be really sad and hard and filled with far too much misplaced guilt. You are also doing the best you can. Somedays your best will be better than others. Just like dogs can be trigger stacked, we too can have circumstances get on top of us.
Patience and forgiveness for yourself, as well as the dog, really does help. And there is much joy to be had.
If you'd find it useful, I'm happy to post links to books etc that I found useful - less for training tips and more for helping me review how I felt about the reactive behaviour. If you already have enough resources and just wanted to vent, that's fine too. Those of us who've lived with reactive dogs know how tiring and upsetting it can be sometimes.