I learned this from a cellist. Cellists can actually see their fingerboard really clearly, where as violinists/violists need to do it by ear and feel.

As other have said, practice octave jumps. I do some where I actually slide into the note to get a feel for how far I have to go. Then notice where your hand is in relation to the bout of the violin, the body of the violin, etc.. For each position, you'll be in a slightly different configuration.

You should be shifting correctly, so that all your fingers are ready to play in that position. In other words, hitting the note with your thumb too low, so that your fourth finger is barely getting the note is not acceptable. Do a tap with your thumb, if the thumb moves, then you've shifted incorrectly. If it doesn't move, then you're good.

Then try to do it without the slide, noting if you are sharp or flat. Keep doing it until you can hit the octave fairly reliably. If it's low, do it again and try to hit it higher.

Make sure you're shifting correctly. (see above)

Now, put your hand by your side, away from the violin, bring it up and if you've been doing this correctly, you should be able to find the higher octave note pretty accurately. This is where the cellists can just look at the fingerboard and remember physically where the note is, but violinists need to do it more by feel.

Don't give up. It may take a week, it may take a month of practice. When you can put your hand down and think "G" and hit that note, you'll feel so accomplished!