Excuse?

I am bogged down by work. My grades are failing. I overslept. I need to focus on my studies therefore it is absolutely fine to skip the training.

The above mentioned are excuses. Palpable excuses. Excuses are a subset of reason, backed by the hope of getting forgiven or excused. In this context, an excuse is an explanation offered to justify an absence or failure in executing something. All excuses are logical, either they try to shirk the responsibility or play the blame game.

"I think I should have done it, but I did something else. So I give an excuse to make myself forgivable and innocent." Well, it is clearly evident I am trying to convince myself and not make myself look guilty. Blaming something abstract even though it is undeniably your own failure to do so is also an act of excuse, due to your act of hubris. This will lead to your downfall eventually.

We have heard of countless cliche excuses like the sudden loss of memory: forgotten, the can't be bothered attitude: don't know, or the universally unacceptable reason: no time. They are unconvincing, albeit they might have some sense in it, and totally unable to justify and validate your own failure. You have to be reliable consistently to pass off an excuse as a reason. Even so, it is contrived and takes a lot of trust from your audience to trust you. If you are late, shows an ignorant attitude or simply cannot be bothered at all, do not waste your time in weaving another fictional story.

There is nothing wrong with giving excuses. As long as it is not given every week in, week out, which makes your absence or failure to look so scripted.
Nothing is wrong with excuses, but using it to escape from failure is a bigbig delusional mistake that everyone should not commit.