Just listen to your body.
If it feels like when you are climbing your lungs are coming out of your chest, then its probably time for a stop and breather until you get fitter. Its not a walk of shame. It may stilll happen when you are fitter, but hopefully past experience will then come into play and you will have more of an idea how hard to push yourself when you get that feeling, (If that is what you want to do).
The same as rest days after riding. As you get fitter and ride for longer, your recovery period after shorter rides will fall away. But in the meantime, if you have sore muscles the day or two after a ride, see how it feels going for a short ride. Might be a relief, or it could be that your legs have no power, so need a bit longer; at least to begin with.
As you spend longer on the bike, play around with the recovery period and your rides. You might find for example, that you can ride 100k one day and on the following day 50k is your limit, without wiping your legs out. But if you have a rest day after the 100k, then you are good for 80k.
There are plenty of training programmes on the interweb and whilst these may suit people, they are only a guide.