I look at the slope of the angle....and compare w/ a right angle (90 degree). I kind of think of it as a mouth and how wide it's open.
To practice what I mean, use your index finger and thumb.....make an L...(90 degree). Then gradually move index finger closer to thumb. As your finger gets closer to your thumb, the angle is getting smaller. By doing this, you'll see how slope affects angle size.
Low (small) slope are usually smaller.
Steep slope (close to right angle) are larger.
Lastly, it may help in many cases to think of the angles as being composed of two sides...one the base and the other the slope. Sometimes, it helps to make the side you think is a slope the base. (Gosh....I hope that makes sense to you....meaning it's easier to compare a different side than what is drawn as the obvious slope side....???) (I'm almost 100% sure that this may sense to know but me...)
I hope I make sense to someone out there. 🙂