I like my smart trainer and zwift for those days I can't ride outside or have purpose to train that can't be easy to do outside. Generally the trainer IS harder than riding outdoor but it's a matter of the quality you put into it. But those easy power days are WAY easier to control than outside world.
Pain adaption is HARD, not just physically but it's mental toll as well. But keep at it and one day the mind will be stronger and the pain will lessen as you get stronger and fitter. I broke 10 bones plus internal damage 5yrs ago going thru a windshield on my bike, pretty much everything supporting my left shoulder was broken. The first hurdle is mental and getting back on it, pain is temporary but conquering it will last a life time. I used to have to take 1/2 norco pill just to keep riding. It sucked and I hated doing it. my HR would drop 10-15 beats and speed was that much slower, lucky to have good friend to keep waiting for me at the hill tops
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Rule #10 // It never gets easier, you just go faster.