In my younger years, I was painfully shy and afraid of others because I thought they wouldn't like me. I actually stood alone a corner for a few years during recess in elementary school because I didn't have any friends to talk to or play with. As time went by, I became a bit of a pushover and an agree-er. When my 5th-grade bully/neighbor showed up at my house and asked me to play outside with her (she actually just circled around me with her scooter and asked if people talked about her behind her back), I said yes and when she continued to bully me throughout summer camp, I stayed silent. This is the kind of person I grew up to be at no fault of anyone -- it just happened.
I used to agree with everyone on everything, and this is when I started making friends. People like a Yes-Man; a person who will tell them that what they're doing is good and the right decision. It's natural for people to want to be lifted up. However, it wasn't good for me or the other person -- I wasn't being honest because I wanted them to like me, and the other person wasn't receiving the honesty they deserved, good or bad.
Around senior year of high school, I started being honest with the few friends I had (two, to be exact). I had a feeling I had made good friends because I was able to playfully attack them with my words and be greeted with laughter or the same kind of remark in response, and this made me comfortable enough to break out of the agreeable nature I had (and in some cases, still do) embrace/d. I didn't agree with political opinions I didn't believe in, I didn't praise a mundane action, and I stopped telling people what they wanted to hear. I didn't become rude all of a sudden, I just stopped nodding and smiling in response. Instead, I began saying, "That's interesting and I see where you're coming from. For me, I think..."
It takes a while to build up the courage to go against what other people agree with and it takes time and repetition before disagreeing becomes more natural and comfortable. But I think it's worth it. Despite the negativity I've felt toward others after a heated conversation, I am relieved I'm at least able to say that I offered my views honestly.
In terms of my fear of being disliked, I still have it. Every time I leave a conversation, I wonder whether I said something that would make someone dislike me. But I'm trying to stay conscious of the fact that I will not be liked by everyone, and it's just the way people work. Some people get along better with others, and for the people they don't get along with, they just have to remain polite and kind to them, and I don't think that's unreasonable. It's better to comfortably share your views and opinions than agree with people and ideas you don't subscribe to, so keep making steps to being fearlessly honest -- I've found that people tend to gravitate toward honest people more than Yes-Men anyway.