Yes, been thru this, too. My son is 15 months old and we first trained him at 6 1/2 months. He's a great sleeper most of the time now. (night time was a dream but naps are often a struggle) My advice is, remember that helping your child learn to sleep is a constantly winding road. Milestones, teething, bad dreams, traveling, house guests, ect. ect. will throw off a good nights sleep and naps. Be compassionate at these times and give your baby the extra attention and cuddling that she needs. Then you can be more firm with the rules to guide her back to a regular schedule. Yes, there will be times when it seems like there is always an excuse to put it off. Once she gets past standing proficiently, you can focus more on sleeping, then she'll master walking, then a molar will come in... Just keep coming back to more firm sleep training when she's ready. Soon she'll 'get' that a regular sleep schedule is the norm, and is what is expected of her, AND that when she needs extra support and a little compassion she will get that from her parents, too.
The other day my son woke up from sleep crying and I thought, oh, here we go, he's protesting, and started 'check-ins'. 15-20 minutes later I noticed at a check in that his hands were in his mouth and realized he was cutting a tooth. My baby was in pain! Then I dropped my 'rules' and went right in, picked him up and gave him some medicine, read some books, and put him back to sleep later.
It's a marathon, not a sprint!
Blessings!
J.