During afternoon work, I usually have a cup of tea as a pick-me-up.

pick-me-up 是由动词短语 pick me up（让我振作起来）演变而来的复合名词。pick 表示"拾起、提振"，me 指"我"，up 表示"向上、提升"的状态。整个短语字面意思是"让我振作起来的东西"，引申为"提神饮品"或"使人精神振奋的东西"。