1.幸福无法取得,happiness 不适合用 get 这个动词；应该说 找到 find / found 比较贴切.
2.语法上完全无法解释,虽然我估计您的意思是“事实上,幸福要靠一个人自己去找寻/找到”
如是,建议您改写为：In fact,one needs to find his (or her) own happiness.