Yep, lion's got it spot-on. Sure, the physical training is
demanding, but what's most important is mental endurance and
determination. It'll be easy to get discouraged, but just remind
yourself - don't. In the end, when you've put on your red beret,
you'll know that it was all worth it.
Prepare yourself for a lot of tekaning as well. Although it seems
that Hendon Camp is a far 'kinder and gentler' place than it was
before, no commando training is complete without harassment -
expect frequent turn-outs, heavy punishments for even minor faults,
getting yelled and screamed at 24/7, sleep deprivation, etc.
There's a certain amount of paranoia that you will have to live
with, particularly in BMT and Basic Commando Training, but as long
as you adopt a positive and optimistic attitude, you'll be able to
cope with the stress.
Since you're going into PTP, try to work on those areas of the IPPT
that you're weak in. Commando PTP is no fun, I had to go through
it, too - but after a few weeks (three, I think, I can't remember
exactly), they conduct an IPPT, and if you clear that, you'll be
able to book out of camp and enjoy a brief holiday before BMT
starts.
And yes, like lion says - at the end of the day, all suffering, no
matter how great, will come to an end. Your first six months will
be the toughest - BMT and BCT are full of harassment. Once you're
past that, though, everything becomes a lot easier, so remember -
just hang in there.
As for pre-enlistment training: like lion says, try to do quite a
bit of running. I would also advise trying to put on some muscle
mass in the gym. And work on those chin-ups!
Hope that's helpful. Welcome to the family, compadre - Honour and
Glory unto thee.