You've been overexerting yourself and taking on more than you actually have time to manage, which is why you've been exhausted.
You've been exhausted because you've been giving everything you do your all, which is exhausting.
You've been exhausted since you've been under a lot of stress and don't want to keep thinking about what may have been.
Since you've been rushing about doing a million different tasks for a million different individuals, you've been exhausted.
You've been exhausted because you've put work and productivity ahead of your personal needs.
You've been exhausted because you won't acknowledge that you need rest and are pretending to be OK while you're actually disintegrating.
You haven't had much time to do much but work recently, so you haven't been able to unwind.
You've been worn down because you've been surrounded by emotionally taxing folks.
Even though you deserve rest nonetheless, you've been exhausted because you believe you haven't worked hard enough to "earn" it.
Since you haven't given yourself enough pauses and have pushed yourself too hard to achieve enormous goals, you have been exhausted.
Because you feel like you need to do more and more, you haven't allowed yourself enough time to rest and unwind, which has left you exhausted.
Even when you have the opportunity to physically rest, you have remained emotionally tense due to your stress.