Have you asked your opponent for a review right after the game? Even your opponent didn’t seem to think they were ahead (and from a lot of very aggressive moves from black, I got a feeling black might be feeling behind in early mid-game)
From the whole board POV, up to move 24 in the opening, your strategy seemed to be taking the corners/territory first while your opponent tried to take the influence on the UL, and build something from the bottom. And black very actively went to the UR and you also seemed to realize it and instead of solidly taking larger corners or sides, chose to accept black’s cut and extend to the center for a fight. Everything seemed to be going according to your plan, when you counter-attacked the cut-off black stones with Q11, and then you tried to make a living for your center group.
Even after tried to escape with the black stones in the upper right corner and you took the black stones to connect the center group, the whole board was still going as your fuseki plan and mid-game fighting direction - take the territory, cut off the invading/attacking stones in two. Black saved the upper side groups by running toward the UL, but as the cost of leaving the right side black group hanging.
I am curious when did you start to feel you were behind? When you simply defend the upper side (which by the way are both alive and not weak, black’s push doesn’t make them weak, in fact helping your groups to live, but leaves a pretty big yose around D19, the difference is like two groups live with about 12 points, and connect live of at least 18 to 20+ points, they helped black connect on the outside, but doesn’t reduce or threaten your groups much). I feel at move 70, you were still following your original plan and trying to isolate black’s left side, and from your description, I believe that’s why you chose to push deep at tengen instead of connecting your stones. Hence, the question you need to ask yourself, if everything was going according to your plan, at which point do you feel you are lacking in execution or judgment?
From POV of the final position or even just a few moves before at move 70. You essentially achieved your original plan you take the corners with UR and LR at least 30 pts with the right side still having the potential to grow. The upper side and UL although small, but around the 10+ to 20 range depending on yose while you have 3 extra captives (4 if you take the stone at move 78), hence you have about 50 pts with potential. And your opponent even if giving all the upper center up to line 12, they are at best 20+ to 25, and the bottom even if all account for black up to the 3rd line are about 30 points, Hence territory evaluation-wise, it is definitely still up in the air (and literally depend on if you can live or connect your center group and erase black’s potential in the air).
If it is a question of whether you are not comfortable enough to make a living in the air with sente? Then you need to work on how to fix isolated groups and perhaps even play high-handicap (>5) games just to practice how to make a living or cut off fighting on the outside toward the center. If it is the part where you feel you don’t have a good enough whole board judgment regarding estimation, then try to replay dan level or even pro games and try to evaluate their territory and positions on your own, and see if your estimated potential matches what those games later evolved into.
And realistically there is no quick path to boost your confidence, and there are always players who are more pessimistic and those who are more optimistic. And ironically most pessimistic players tend to like fighting a lot. If you are a territory player and still pessimistic, then you definitely need to play more aggressively. Learn how to use your early advantage to push through your opponent’s outside influence or how to prevent them from forming in the first place.
