"Me alegro de que..." vs. "Me entristece que"

Question

What is the reason that "Me alegro DE que..." is constructed differently than "Me entristece que...."? Do other similar phrases tend to follow one of these two patterns?

Silvia Píriz · Accepted Answer

Hola Claire J.
The difference is simply due to the way these verbs are constructed. Some Spanish verbs require a specific preposition before a subordinate clause, while others do not. Alegrarse is one of the verbs that requires the preposition de, so we say:
Me alegro de que hayas venido.
On the other hand, entristecer(se) does not take a preposition before que, so we say:
Me entristece que hayas venido.
Unfortunately, there isn't a general rule that lets you predict which verbs require a preposition. It's something that has to be learned along with each verb, much like English expressions such as depend on, believe in, or listen to.
Other common verbs and expressions that follow the same pattern as alegrarse de include:

arrepentirse de que...
estar contento de que...
sorprenderse de que...

Whereas verbs such as entristecer, molestar, preocupar, gustar, and encantar are followed directly by que.
So the difference isn't related to the use of the subjunctive, but rather to the individual verb's required construction.
Saludos
Silvia