sorry for wtl;dr
Since the death of Khal Drogo, pretty much everything Dany's done has been a success, or has led to a success.
Let's start with Dany at her peak, Ruling Mereen, worshipped by its people, breaker of chains, Has all 3 dragons
Immediate "family" - Jorah Mormont, Barristan Selmy, Missandei, Grey Worm, Daario Naharis - all loyal unto death for her and have been for years.
New advisers: Tyrion Lannister, Varys - both with extensive knowledge of Westeros and determined to help her retake the throne, but definitely not willing to die for her.
Descent to the Mad Queen
Incident #1 - Barristan Selmy killed by Sons of the Harpy thugs in an alley brawl. Loses her most true father figure.
Incident #2 - Sons of the Harpy attack the arena and slaughter hundreds, while she escapes on Drogon - citizens lose trust in her.
Incident #3 - She leave Essos behind to retake Westeros, leaving Daario Naharis behind - her lover and confidante who does not judge her at all, and provides easy comfort.
Incident #4 - Against the strong advice of her Hand, she burns the Tarly Lords when they won't bend the knee. Very akin to what her father preached instead of taking hostages.
Incident #5 - Viserion dies at the hands of the Night King. Her invincibility factor by dragon no longer exists, and she has lost 1/3rd of her children.
Incident #6 - She travels to Winterfell and finds not everyone wants to accept her as Queen or even like her. This is after she has collected the Unsullied, the Dothraki, and made alliances with Dorne, High Garden, the King of the North, and the Iron Islands who have all bent the knee to her.
Incident #7 - Jon Snow reveals he is really Aegon Targaryen. Instead of being her strongest ally and paramour, replacing Daario Naharis, she now doesn't know what to make of him, and fears he could be a rival for her claim.
Incident #8 - Jorah Mormont is killed by wights. Now she has no father figure at all. Tyrion Lannister and Varys might be shrewd, but they are poor replacements for Ser Jorah and Ser Barristan in terms of the support she has come to rely on.
Incident #9 - The Army of the Dead is defeated with very little help from her. Drogon can't kill the Night King and her two main armies are largely decimated. Two players younger than she is - Bran and Arya - combine to kill the Night King with one distracting him and the other ending him. Attention is lavished instead on Jon Snow / Aegon Targaryen, and even her advisers begin to question if he might be the right choice to sit the Throne.
Incident #10 - An ambush decimates her fleet, kills Rhaegal and sees Missandei taken hostage. She is outsmarted for a second time by Cersei/Euron and is down to one dragon now.
Incident #11 - She watches Missandei be executed by the Mountain. Her only female adviser is dead, and perhaps her only real friend as well. The death affects Grey Worm as it affects her. He no longer wants a life beyond the war. He has become vengeance, and will gladly go to his death if it means slaughtering the people who killed his love.
Dany is now alone with a military commander she knows is out for blood like she is, two advisers who are questioning whether she's fit to command, and a sort of boyfriend but also your nephew, who swears he doesn't want the crown, but whom she can't believe. And his great secret, once known only by her, him, Sam, and Bran, has now stretched to Sansa, Arya, Tyrion, and Varys, except she doesn't know that they know.
On the flip side, every one of her greatest successes has been born out of fire.
#1 The birth of the dragons
#2 Acquisition of the Unsullied/death of the slavers
#3 Escape from death at Vas Dothrak and having the Dothraki serve her without question
#4 Victory at the Battle of Slavers Bay with all three dragons unleashed
Fire could not beat the Night King, but it can surely burn Euron Greyjoy's fleet and destroy the Red Keep and Cersei with it. Her string of recent events will have her doubting every strategy but the one that her family is built on - winning the Iron Throne with fire and blood.
