Originally posted by: Shaavi
 
Mahua, I would like to share a couple of my personal experiences. When my son was around 3 yr old, he fell from the countertop of our apartment. He was naughty but hadn't thought that something like this would happen. His arm got broken. We went to emergency and they did surgery to put his hand back together. He was lucky that his hand was fixed with minor surgery. So when we brought our home, even though my husband wanted to get hardwood flooring, I went with carpet. I kind of enforced it that we will have carpet and not hardwood. The reason was my "fear" of him getting hurt. I was scared that he would slip from the stairs or fall on the floor and get hurt. 
The other one is my daughter. Before she was born I was unlucky and had 2 - 3 miscarriages. So when I found that I was pregnant, it scared the heck out of me. But the fear didn't leave me even after she was born. It used to take a lot of mental effort to carry her from the bedroom to family room on 1st floor. I used to walk towards the wall away from railings. I was scared that I might accidentally throw the baby over the railings. Both these times it took a long time for me to come out of that "fear". My husband helped and I myself had to tell several times to myself that everything is going to be ok. Now even though I don't do helicopter parenting and fuss over them, I lot of things still scare me. There are times when my heart goes to panic mode and I have to calm myself. Fear of losing is very real especially if you have lost multiple times.
The Dev we are seeing is the one from the beginning of the series. The one who was ready to give 30% shares of his company to a guy because he had agreed to marry Neha with her conditions. He went through great lengths to hire Sonakshi as the nutritionist for his mother so that she can be healthy and happy. He is also the guy who meddled in Sonakshi's life without waiting for her to say yes or no to Kushal. He was the one who made absolutely sure that Ayaan never came back in their lives. He was ready to wait 5 hrs in the cafe to say thank you and sorry. He is a guy who thinks more from his heart than from his brain. He has seen his family struggle since his childhood. At those times he would get frustrated that he couldn't do anything to reduce it or give his family what he thinks they deserve. From his perspective now that he is all grown up and able, his family needn't worry about anything. All they need to do is let him know what makes them happy and he will get it for them. 
The other most important thing is what Sonakshi means to him. She is like the parrot in which the sorcerers life resided from the fairy tales I used to read as a kid. You know in those stories it would be like the magician kept his life in that parrot and then left the parrot in a golden cage in the cave of an island far far away. So that when his enemies attacked they wouldn't be able to kill him. Just like that Sonakshi is Dev's life. He knows that he will stop living if anything happened to her and will never be able to forgive himself. What he saw in the bus and has shaken him to the core. The "fear" of what could have happened has gripped him body and soul. 
Sonakshi might know only some things about him, but Dev knows everything about her. During Dev remarriage track, when Ishwari tells him that she started this talk only for Sonakshi to confess her love and come back, Dev says the reason she is not coming back is because of her. He also continues saying that Sonakshi had wanted to "win" everyone's hearts and they made her lose. Even when Ishwari goes to talk to Sonakshi during Dev's engagement, she also says the same thing. That if you come to IN this time it has to be your choice and your win(don't remember the exact dialogue, but Ishwari says this that Dev wants her to choose, to win).
 He dreads to think what might have happened if he was a couple minutes late or if something had happened to Sonakshi. He is kind of holding himself responsible for it. He feels guilty that he couldn't stop that from happening. His thought process is something like this. If Sonakshi had not gone it wouldn't have happened. She went out because she was looking for investment that will make her company grow. It will make her "win", achieve her goal. If he had paid attention earlier and ensured of this investment, it wouldn't have been necessary for her to go out. So he is trying to eliminate the root of the risk. Since she is his lifeline, he wants to make sure that she is safe at all times. And for that he doesn't want her to do anything that might put her at risk and wants to eliminate anything he perceives as harmful for her. 
From his pov, Sonakshi has struggled a lot already. There is no need for her to do anything when he is around. He wants to make sure that she gets only happiness in her life and she shouldn't see anything negative like pain, fear etc. in her life. If winning is what makes her happy, then he will make her win. For him she needs to be smiling and not have any stress and then he will feel better about himself. And it also ties back to Suhana's question, how will you keep me happy if you couldn't keep mommy happy. He is now going for that protective trait where if it were up to him would not let her venture out of their room let alone home. What he is trying to do is remove anything that seems like something that can harm her. or give her pain. He wants to surround her with only happy thoughts and things so that she can be happy and never want to go somewhere without telling him, leaving him. 
He never dealt with the trauma of losing the people he loves in his life. He feels that he couldn't keep them safe. Now since Sonakshi is his life, he is trying to build a wall around her so that no one can hurt him. What happened has shaken him to the core and he wants to protect her at all costs even if it is against her will. He will buy her happiness if that is what it takes to keep her with him. 
This is Dev's love for her that has taken hold of him and the possibility of losing her is making him do and say the things he said.