What is the real meaning of letting nature take its course?

The general meaning of the whole sentence is to let nature take its course. Some things can't be forced, destiny takes a hand.

You can do whatever you want, which means whether you are seeking marriage, career or other things, you should let nature take its course, do your duty well, focus on what you can change, persevere and stick to it.

Let it be. It is the same meaning as the above sentence, which means to do what you can and leave it to fate. In other words, do what you can, don't force it, and leave it to fate.

Don't sigh that everything in a year is not satisfactory, you will find that everything you ask for has come true inadvertently.

The whole signing is not to make any changes, stick to the previous lifestyle and way of doing things, accumulate quantitative and qualitative changes, and you will succeed one day.

This signature does not mean that everything is destiny takes a hand, and no effort is needed. What he means is that you need to do your best to fight for your ideal, but don't rush to achieve it. If you want to succeed, you will succeed if you accumulate to a certain extent.