I'll add my 2c worth (FWIW I'm well towards the other end of my career):
7. ATC is a complex job in that you need to perform reasonably well across a range of skills, consistently. Whether you can pull them all together to a high enough standard and consistently enough is what's tested in the sim - whether you've "got it" or not. Yes, training helps to an extent but mostly it's from within. As Whispr says you need to put in the hard yards memorising standards, etc. as well.
Listen to the instructors, particularly in the field. Listen to other controllers giving tips. Yes you need self-confidence but it needs to be tempered - they're telling you these things for a reason. I've seen trainees go down for no other reason than over-confidence. Occasionally a trainee can't abstract themselves from the number of lives they're dealing with so find it too stressful.
Be aware that gaining a rating isn't the end - you need to keep learning and showing improvement to retain the rating. Most people naturally do but occasionally not.
ATC isn't the job for everyone and as Whispr says the reality sometimes just doesn't work with personal/family circumstances or priorities. You'll miss out on kid's birthdays, Christmas dinner, family events, gatherings with friends. There will be bad days during the training (and occasionally on the job) but you just have to push on or you will get left behind. Learn from them but don't dwell on them - ATC is a confidence "game" and if your head isn't in the right place no amount of ability will help.
If you can overcome/cope with all that it's a great job.