Try to use this lesson and apply it towards getting your 19 month old into a routine now. If you have anymore kids, the best thing to do is get them into a routine from the very start.
It's something that you'll have to either decide you want to fix or decide that you're going to let it go. Because the process of fixing this is very hard. With my kids, I never let them fall asleep outside of their cribs, of course that wasn't the case for the first few months though. If my baby started falling asleep, I would sit them up to wake them slightly and then take them to their room and lay them in their crib. That way, they identified their crib with sleep. Because of doing this from the beginning, they learned that when I laid them down, it was time to sleep. Now, with my first, I didn't do this because I was never told to do it that way. So, I had the same issue as you. She was 15 months old and I had my second and realized that the rocking and walking her to sleep wasn't working anymore because I had the newborn too, and it seemed like while I was rocking my first, the newborn would cry and wake her up. So, I was forced to break her into a new routine. I started out by laying her down for her nap in her bed. She didn't like it one bit and would cry and cry. I let her cry though, and after 3 days she would go to sleep with either no crying or very little crying. Nighttime was a different story. It took her about 5 nights before she really got used to it. As a matter of fact, she would get so worked up that she would literally throw up. I would just wait until she went to sleep to go in and clean up. Since she was always standing while she was crying, she only threw up a little over the rail onto the floor. I know, it sounds horrible, and I hated it, but my pediatrician told me that "she had ME trained, and I had to take the control back". I realized he was right because after all, I was the parent and the one in control, not her, and I had to change things around so she realized that. I'll tell you what though, it's well worth to have stress free bedtimes for only 3-5 nights worth of work. People will say to not let them cry it out. They will say that it's damaging to their self esteem and all kinds of stuff. My daughter was so much happier though after she was in a routine. She was crabby before that, and very demanding also. Kids NEED structure. They NEED limits, and they especially need a schedule. Once I got her into a schedule, I was AMAZED at the difference in her throughout the day. She was in general just happier and less crabby. Now, she's 5 and has wonderful self esteem, is a wonderful sleeper, and respects me. At bedtime, my husband and I take turns putting our kids to sleep, and the whole process takes about 2 minutes. After that, they sleep all night from 8 until 7 or 7:30. I'm telling you, fix it now and enjoy quality time with your husband again after the kids go to bed!!!!!!