Later on in our relationship we started to drift apart because, being a student from Canada, I had a lot of problems with Portuguese which led to my failure at the end of the school year.

drift 本义是"漂流、漂移"，这里比喻人际关系逐渐变得疏远，像船慢慢漂离岸边一样。 apart 意思是"分开、分离"，表示物理或情感上的距离。 drift apart 是一个固定短语，指人际关系逐渐疏远，感情变淡，通常是一个缓慢而自然的过程。