Sleep Training & Emotions

I am feeling a lot of different emotions about this sleep training thing. 

Last night, M did awesome.  David finished the bedtime routine and he put M in his crib.  M didn't cry once - he "talked" to himself for 15-20 minutes and went to sleep.  Today was a different story.  Had a great morning and walk and then I laid him down.  He didn't cry .... until 10 minutes later.  Then he wailed for 25 minutes before falling asleep. 

30 minutes later ... he was awake.  This is his "nap routine".  I can't figure out why he isn't staying asleep for his naps.  We have tried letting him cry and now we are following the advice to soothe him back to sleep.  I am not sure what our next step is. 

I was hoping to get him napping well (on his own) before heading back to work but I am not sure that is going to happen. If I can be honest, I don't think that it matters that much as Grammy & M will do their thing but it's like I needed a project to occupy me (us) before I head back to work.

Feeling sad about leaving him...I know that he will be fine but, to be frank, I am jealous that someone else will get to spend the days with him while I am with other people's kids. He is just so much fun and all I want to do is play with him and watch him figure things out. It just makes me sad.