Every so often as I go through Duolingo Spanish lessons, I hit a wall.
Right at the start, for example, I had some trouble with present-tense verb endings for first/second/third person. But once I got that (mostly by remembering Latin amo/amas/amat and dropping the final t from amat), it was pretty smooth sailing for a while.
Then I reached a point where a lot of the new vocabulary consisted of words that didn't have obvious English cognates (and that I hadn't learned by osmosis growing up in California), so I was having trouble learning them. But I eventually got through that part of the tree too, partly by looking up etymology in Wiktionary. And then everything was good for a while, and I was feeling like I had a pretty good handle on this Spanish thing and it was mostly just a matter of expanding my vocabulary.
And then I hit object pronouns and reflexive verbs, and was completely at a loss.
After days of struggling with that and getting almost everything wrong, I started to write up my conceptual confusion in the form of a plaintive query to post somewhere asking for help, but somehow halfway through writing that up, something clicked. And I followed a Duolingo-discussion-page link to a useful page about reflexive verbs and pronouns, and it all started to make sense, though I'm still not great at remembering which pronouns to use where and which verbs are reflexive.
So I moved on, but before I could get back up to full confidence, I plowed headlong into past tense, which is not only introducing a bunch of new verb endings, but also a bunch of new verbs, most of them without obvious English cognates. I went through that lesson very slowly, and will be going through it again soon to try to remember more of it. (I keep trying to remind myself that a lot of what I do know is due to repetition; I don't have to learn everything on first exposure to it.)
And I'm still less than halfway through the full Duolingo skill tree, which I suspect means that there's a lot more hard stuff yet to come.
But on the plus side, I've done at least a little Duolingo almost every day this year. And it says that my Spanish fluency is at “49%,” which on the one hand is ridiculous (I'm nowhere near halfway fluent, not even in reading, much less in writing or hearing or speaking) but on the other hand, I can read a lot more of things like bus ads in Spanish than I used to be able to.
Anyway, I doubt I'll ever be really fluent, but I'm very pleased that Duolingo provides such a useful and me-compatible service. (My goal from the start has been to learn a little more Spanish, rather than to become fully fluent, and by that measure I'm succeeding.) And I hope to continue to, very gradually, get through the harder parts.