How to deal with anxiety caused by dangerous riding conditions stemming from poor lane design and inconsiderate fellow road users? Location is Belgium.

I stopped seriously riding my bike about 5 years ago. At the time, I used my bike for commuting to work for about 9 km one way. The main reason I stopped was because the timing and route of my commute brought me through various situations that I did not enjoy at all:


My home is within 100 meters of a high school, and during my morning commute, I had to drive on a bidirectional bike lane which leads to this school. However, I rode away from the school right during the rush of students riding to the school. These students often drove side by side on this lane, while there was only barely enough room to comfortably pass each other on the lane. There were multiple times where I skimmed the shrubbery on the right side of the lane very closely, almost to the point of crashing into it.
Midway through the commute, I had to drive on another bidirectional path with barely enough room for comfortable passing of oncoming traffic. However, in this case the non-street side was a foot deep open sewer with a lot of overgrowth on the other side. There were some places which had regular growths of hogweed at roughly handle height. Hogweed, for those unaware, is a plant that can cause inflammatory reactions if it comes into contact with the skin. The street side wasn't much better: there were a lot of parked cars, some parked so close to the lane that at times I had to swerve to avoid running into a side mirror. In addition, the lane was VERY poorly lit at night and even somehow had a sign partially obstructing it about halfway through. To top it all off, in order to get on this lane, I had to go through a bike tunnel under an elevated highway and take a 90° turn left, both sides of the bike lane obscured by the sides of the tunnel.
About 500 meters before I arrived at work, I get to another bidirectional bike lane. this one was short, but it was a VERY curvy path where you can't go fast, it's again barely big enough for 2 bikes to pass each other, you can't see around corners because of a 2 meter high hedge on both sides and it's quite busy. I again had a few incidents with skimming or even landing in the hedge on the side because I had to evade an oncoming biker I didn't see coming.
Along the entire path, there were a couple times I had to cross intersections with no traffic lights, some of them quite busy. I had 2 incidents at one of these intersections, one of which severe enough that my back wheel got bent out of shape and I had to bring my bike in for repairs.
Finally, a lot of cyclists along this way were really driving quite dangerously. I've already mentioned the teenage cyclists driving side by side on a lane that isn't wide enough for that, but there are others: cyclists who don't use a light at night (though I sometimes made this mistake too) or actually a blindingly bright light; cyclists overtaking other cyclists on busy lanes; Cyclists that drive too close to the center of the lane to safely pass them; cyclists that are using their phone while cycling and aren't paying attention; Cyclists that cycle very slowly in a lane where you can't safely overtake them; Even people walking their dogs on the bicycle lane.


All of this and more at the time really gave me a whole lot of anxiety about cycling, in addition to the higher amount of stress I was already experiencing from working a day job that fit poorly with my autism. I already wasn't too keen on cycling and running into these problems on a daily basis really caused me panic, stress, anxiety and so on, to the point that almost exactly 5 years ago, I gave up on riding my bike to work and switched to public transport. Since then I only rode my bike recreationally, and even then only incidentally.

I don't plan on cycling again in the foreseeable future, but if I were to one day start cycling again, what can I do to reduce the chance that I run into these issues again?
1 Avoid obstacles
There's not too much you can do about this. That school almost next to your home means you'll always be stuck in student-rush hour no matter what you do. Except maybe if you can go around the school area in a relatively small detour. Cycling on a quiet parallel road may be well worth the extra few 100 meters.
2 Be noticeable
Wear high visibility clothing (fluo vests, reflectors, clear lights when it's dark). Especially useful when the other cyclist isn't visible. At least they'll clearly SEE YOU and will evade you.
3 Loud bell
Get yourself a nice loud bicycle bell. One that you can hear from a couple houses away. Use that bell any time there's someone blocking your path, and use it early. Don't wait till you're right behind them. If you ring your bell early they should have just enough time to look behind them, see you and move out of the way when you reach them.
This one works really well if there's someone walking their dog. Given enough time they'll move their dog besides them and maybe force it to sit down, or at least in a position where they can safely keep the dog away from traffic. You might still have to slow down a bit to safely pass them.

Someone riding middle of the bike trail? -&gt; ring your bell
2 people riding side by side not leaving room for you to pass? -&gt; ring your bell
pedestrian not really looking taking up too much space? -&gt; ring your bell
someone driving unsafe with cell phone that you can't pass -&gt; ring your bell

Moreover ringing before a turn with no visibility is the only way to make your presence known without a mirror or stopping. (This is actually the main and intended use of car horns in a lot of countries)
Most of the times (sadly not 100%) they'll make room for you to pass safely when they hear a loud bell ringing.
4 Plan for slowdowns
You mentioned autism. A lot of your anxiety might come from not being able to ride at your expected pace to deal with those &quot;unsafe&quot; situations. If you plan on slowing down at least 10 times during your ride, some of those close to a standstill, and leave enough time to arrive at your destination in time it might take most of that anxiety away. (Note: I don't have autism myself and have only a bit of experience with coworkers/family members on the spectrum, not sure if this hint really works for you).
5 Get used to cycling in calm situations first
Instead of forcing yourself on a fixed hour to get to work in time. Try going to a grocery store in the weekend on a bike to get some minor supplies. You can plan this small trip on a slow hour when you know there'll be few obstacles. If you can't get used to the short bike trips that way, you're probably better of using public transport instead.
Final note
Although most people on this stack will likely not agree with this statement I still think it's true for certain people:

There's nothing wrong with not riding a bike.

I have an uncle that never learned to ride a bike. He always got everywhere he needed and is happy that way. If you don't like riding your bike then don't ride your bike. Public transport in Belgium is usually good enough (although not optimal) to commute to work and even do grocery shopping or visit family members.