I don't know if this has happened to you much, but I usually play slots from time to time and when I get free spins I usually win something, sometimes more, sometimes less, but I always win. Today I got two rounds of 10 free spins playing Wild Bounty Showdown, and in the first one I didn't win anything, while in the second one I won about $0.34 (playing $0.20 spins). I felt a bit silly, because getting free spins is cool, it's usually exciting, and I've won some good big wins a few times.
Your spin luck is crazy man, free spins play like total freebies, IMO that win always feeling is just an RNG trick. Casinos will crank out wins in the bonus round to get your attention, but slot will slow down, then it's back to stacked odds on the casino's side. It's not magic, it's math, house edge and randomness making those occasional free-spin wins just dummy noise. So don't beat yourself up, slots are designed to tease you with a couple of wins, then shove you. Dont be serious to grab huge money, Let's just keep it fun, fam.