form & within yourself?

[Eway]

Reading a book called Running for Peak Performance:

"When setting yourself a reasonable goal for your first run, don't worry about speed or form: time is of the essence. You should simply aim to jog for as many minutes as you feel comfortable and 'within yourself'."

Does "form" here refer to running posture? ( I think "running" is already the "form". Why would he say don't worry about form? )

And, what does "within yourself" mean?

[Casiopea]

"When setting yourself a reasonable goal for your first run, don't worry about speed or form: time is of the essence. You should simply aim to jog for as many minutes as you feel comfortable and 'within yourself'."

"form" refers to the way you run; e.g., arms bent, back straight, etc.

"aim to jog for as many minutes as you feel .... within yourself" refers to how much energy you have within yourself to continue jogging.

[Eway]

Thanks!

And from the same book:

"When you start running, a good rule of thumb is to run easy and follow every day you run with one where you do not - in other words, a rest day. You will be recovering for the first time in years, maybe ever, following these initial runs."

I don't understand the sentence in purple. Is it saying that you can only recover after many years have passed? And, what does "maybe ever" mean?

[Casiopea]

On your rest day, you'll be recovering from the run you did the day before. If you are new at jogging, your muscles won't be used to the work-out, so your muscles are going to hurt a bit the next day. That's why you need to rest every other day. You need to let your muscles recover - get back to the way they felt the day before.

"maybe ever" means, possibly you've never before felt what it's like to have tired muscles. <It's an experience! The first time I started jogging, it felt great, but the next day ... AGH! The pain! My muscles were so very stiff and sore!!> I needed a day of rest before I could jog again.

[Eway]

Still confused...
If it's talking about rest "day", why would this sentence have this term "in years"? The years here refer to the years when one was not running or...? The rest day is the first time you recover since all those years you were not running?

[Casiopea]

It seems to me that the writer is talking to people who are new to jogging, people who have never jogged before. Now, if you haven't jogged, and you start, then your muscles are going to be rather sore the next day. The reason being, you probably haven't used those muscles in that way for many years; i.e., in years, or possibly never used the muscles in that way until now, i.e., maybe (n)ever, and so your muscles are going to be sore, rather sore, and need a day of rest to recover.