Pretty much what everyone else has said so far, I'm just gonna repeat it in my own words and add a bit because I like to help people who have had or are having struggles which used to trouble me as-well.
Think why you get ladder anxiety. In many cases its because of the time you spend on the game and a specific goal you have set for yourself. Many people set the wrong goals. In the case of League the wrong goals are divisions. Don't set a goal like "I wanna be gold 3 by the end of the week." Such goals are wrong and are only going to hold you back as they will cause more ladder anxiety.
The reason they are wrong is because it is not always in your ability to climb the ladder and some games are just un-winnable by a player of your skill level. I'm not saying its your team's fault every time and that they are holding you back but losing promos can be really demotivating if you have set yourself such a goal.
Instead try to set goals which you and only you can control the outcome. Such goals are usually improving at aspects of the game and the outcome only depends on how much you are willing to try and reach that goal. Not a single person other than yourself influences these goals and there are no excuses. Hence when you queue up for a game its good to think, this game I'm going to have 70 cs by ten mins and always have a ward on one side of the river for example.
From your post I realise that you are influenced by comments other people do on your gameplay. Now its fine to totally ignore these comments, after all its your time and you can play the game as you want. No one expects anything from you and you are playing for fun. A part of me also tells me thought, that you want to improve at the game and climb the ladder. Hence these negative comments should not be totally ignored as long as (and I put a lot of emphasis on this) they involve your gameplay and nothing else. Negative comments in my opinion should be ignored in game, should never be answered back (never hit the reply button) but should be kept in mind as a reminder that I am doing something wrong.
Lets say you are playing mid and you die to a gank. No one should say anything because most probably you simply got outplayed/ baited into thinking its safe and overextended. But if you die again and a comment pops up saying "damn this midlaner" or "gg" then know that you are doing something wrong. Its wrong for that comment to come up in the first place, as they should simply say nothing or just "hey mid, maybe u can ward river?" but that's how the game is in these lower elos. You can either mute everyone from the start, or when the comment comes up, just know that something is not correct in the way you are playing. (unless of course its the typical stop focusing the tanks noobs comment but I'm not gonna bring that one up).
I'm now gonna bring up a similar example from one of my latest ranked games. I was playing ori and my enemy kat was simply outroaming me like hell. Was she better that me? Yes. Did I get flamed? Yes. Did I play perfectly? No. After the game I asked myself how come after having a pretty much free lane, I had the same cs with kata at 15 mins and I was never able to tell my team that she is roaming to ping them back. The second one is pretty clear, my map awareness is lacking. For the first one I went to the replay and saw that my mana bar was constantly low when I was in lane meaning that kata was able to outpush an orianna (lol) and I was always stuck at turret when she got free roams. So I learned that I need to improve on my map awareness and also time my recalls better. If the criticism had not come through I might have accepted the loss and and left it at that, thinking that kata naturally outroams ori and there is no counter-play. So criticism is not necessary a bad thing as long as you don't take it to heart and become too emotional about it.
The other thing you mention is that you failed your gold 4 promos many times hence you didn't want to play ranked when you were gold 4. Two points arise from this.
First you should care less about the rank you are in. In the end it doesn't matter as it was only a system implemented by Riot to mask the old elo system. Basically elo still exists but it is hidden behind the division names. As others have said stop caring about LP. Be prepared to lose some if you want to improve. When learning a new champion the way you usually want to go is watch some montages, pick him in a few normal games and then go ranked (imaqtpie stream). Yes you are going to lose some games but that's OK because you will improve. That brings us back to the goals I mentioned earlier and why your goals should not be divisions but actual improvement at the game. Losing might not help you reach that shiny plat/ diamond border we all want in the short run, but hell, it will help you improve and achieve that border in the end.
Second and pretty similar to the first point don't be afraid/ anxious of playing vs. better players. The reason is the same as above. You will lose but you will have learned more that what you would learn from stomping a low level enemy, who plays predictably and is easy to outplay.
Well this got pretty long (oops) but I hope it helps you become a better player both mechanically and mentally, as both are really important aspects of the game. :D GL HF hope I play with/ vs. you soon!