How old is your baby? Newborns are not able to fall asleep alone, and they might wake up once you put them down because they sometimes have just very short sleeps and they prefer contact napping. Practicing drowsy but awake is ok from 12 weeks old, from then it's possible to teach babies to fall asleep on their own. My boy is now 1 year old on the 18th, we sleep trained him at 4 months, started sleeping through the night by 6 months, but he was still crying in his sleep a crazy lot, just bow starting to actually sleep good, and for his afternoon nap I usually rock him on me because otherwise he would fight and scream very hard because he doesn't want to stop playing, but at night he is so tired that now he falls asleep on his own in like 1-5 minutes after I put him in his crib and sleeps until at least 7 am