Wolfgang Köhler hung a banana out of reach of the chimpanzee, Sultan. Sultan strived to get it. At first, he didn't use much effort. He reached for it, but his arms weren't long enough. He began to jump. He put in more and more effort and jumped higher and higher, but was unable to attain the necessary height. Finally he pulled boxes underneath the banana, piled them up, climbed on them, and got the banana. His endeavor was successful. The planning and logic needed to attain his goal were an impressive achievement for a chimpanzee.

One difference is that attain, strive and achieve are all verbs; effort is a noun; and endeavor can be either a noun or a verb. Another difference is that some relate to trying hard to do something, but don't imply success, but others have to do with success. "Strive" means to try hard, and so does "endeavor" when used as a verb. "Effort" is also means trying. But you can strive or endeavor without success, and you can put in effort without achieving success. But "attain" and "achieve" both mean to reach or have success. "He attained his goal." "He attained the rank of General." "He achieved great success in life." Sometimes you can attain or achieve something without effort (for example, just though good luck).