i don't know. Just try

My brother, the more you think that you are stuck the more stuck you will be. It is like the chinese finger trap, the more you pull, the tighter it gets. What you should do is just relax a little. When you come across a problem, just think. Don't stress over the problem. Don't think that you are stuck or stupid if you can't solve it. Even if you think about a problem for hours and can't solve even an easy question, it doesn't matter. If you stress over it, you won't enjoy it. And most importantly, you won't learn from it. So this is what you should do:

First of all, only try problems with editorials. If you try problems without editorial and can't solve it, it will live on your mind like a parasite and you won't be able to relax. This will be very bad for your learning.

Next, when you are solving a question, just let your mind wander about different possibilities. It is very important, especially in contests, that you don't think about the amount of time that you have left. Time only stresses you out and stress doesn't let your mind be creative. In general, remove anything around you that is pressuring you or stressing you out.

Finally what you should do, is the next time you try a problem, take a few deep breaths and just think about it. Think about it like you would think about any other problem you come across in life. It is very important that you don't stress over the problem as this will hurt your mind and your learning.

I was thinking of giving you an overall tip about constructive questions but I won't because I feel like if I do that then that's all you will think about the next time you try a constructive problem which, when doesn't work, will hurt your learning.

So, good luck i guess.

Edit: I left out the most important thing which is this: DON'T CARE ABOUT YOUR RATING. What I mean is that becoming smarter and becoming better at solving questions won't necessarily increase your rating in 1 or 2 contests. It takes place over a long time. If you just focus on learning, relaxing, and not stressing yourself (as I explained above) your rating will eventually increase. So don't look at your rating too much. :)

1. Just grind constructive problems, preferably in the 1200-1700 range if you want to get the question A, B, C in div 2. You won't get better at constructive problems if you grind Graph, Segment Tree problems.
2. Just relax. Most of my constructive problem in a contest (problem C div 2) was solved when I was going to the toilet, so yeah, just relax, let your mind wander, and you will got it.
3. Don't emphasize rating too much. You are literally green, there's nothing to lose.

The only way to improve in constructive algorithm is to practice constructive algorithms. You have solved a good amount of question of rating 1300-1500 so go to problemset, set difficulty to 1400-1600 then go to add tag and select only constructive algorithm and practice.

Try to solve more problems (by yourself) or learn from editorial and resolve

quick question: Why constructive problems are trendy ?

Just try many many many ideas. Just throw them, usually there is one that solves the problem. To have a lot of ideas, you need to solve problems on these ideas. So, just solve problems, I recommend solving problems whose complexity is 200-300 points higher than your rating.