Because learning a second language (L2) is difficult, manylearners start with easy words that look like their native lan-guage (L1) to jumpstart their vocabulary. However, this ap-proach may not be the most effective strategy in the long-term,compared to introducing difficult L2 vocabulary early on. Weexamined how L1 similarity affects pattern learning in L2 byteaching English monolinguals either an Englishlike or Non-Englishlike artificial language that contained repeated patterns.We found that the first words that individuals learned in anL2 influenced which words they acquired next. Specifically,learning a new word in one session made it easier to acquirea similar word in the next session. L2-similarity interactedwith L1-similarity, so that words that looked more like Englishwere easier to learn at first, but they were less effective at in-fluencing later word learning. This demonstrates that althoughnative language similarity has a beneficial effect early on, itmay hinder long-term learning by decreasing recognition of re-peated patterns within a second language. This surprising find-ing demonstrates that making early learning easier may not bethe most effective long-term strategy. Learning difficult vocab-ulary teaches the learner what makes the new language unique,and this general language knowledge about language structureis more valuable than the words themselves. We suggest thatdifficulties during learning are not always to be avoided, as ad-ditional effort early on can pay later dividends.