Learn English – what’s the word for when you don’t resist doing something you don’t want to do

What's it called when you unenthusiastically do something that you have reservations about. You might consciously resist participating in something because you're ethically opposed to it or because it conflicts with your personal ideals. But in the end you submit either because you're compelled by duty or obligation, you realize your ideals aren't pragmatic, or your method keeps failing, or you realize you were wrong. Whatever the reason, you might not be happy about it and you might not want to admit it, or maybe you're simply being forced. But in the end you relinquish control or subdue your inclination to resist, and you cooperate or comply.

An example is, you might be a passionate, publicly outspoken opponent of euthanasia for many years; adamant that your way is the best and only way until a day comes that you have to watch as someone dear to you suffers.

Another example is, you might be in the military, and your commanding officer gives you an order to do something that you disagree with but you decide to just grit your teeth and do as you're told.

It's a word that I learned only recently, and I have used it in context before, but have forgotten. I believe it's a verb. Actually, I recall there being two similar, but distinctly etymologically separate words that both can be used to basically mean the same thing.