If its tiring for you to mew, you are probably not doing it correct. If you can get most of your tongue on the roof, it will stick automatically because it creates a suction cup. You are not meant to walk around pushing all day long. 

Personally I get tired and lightheaded just because I started mewing 3 days ago and find it hard to breath through my nose if doing it correctly, but I know eventually it will get easier as many have stated here on the site. The trouble is finding that balance between mewing enough so that you're lifting the back of the tongue against the soft palate but not too hard so that it completely restricts airflow.

Im no expert, but if we are talking about the same soft palate I dont think thats what you should go for. If I put my tongue on the soft part all the way in the back, I will allmost choke on my own tongue, and its a very awkward position that I could never keep 24/7. 

There are plenty of videos explaining how to do it well out there, your tongue should be pressing up and forward. If you press on the soft palate you are allmost pushing backwards, and restricing your airflow - your not supposed to do that.

You definitely want to be hitting the soft palate if possible. The back of the tongue is the most important part of tongue posture. If you push hard on your palate with your tongue and your under-jaw area bulges, you are doing it wrong. The tongue ought to be as far back as you can get it

yeah man sometimes overthinking just makes it worse. just do this https://www.youtube.com/watch?time_continue=10&v=VuCCIE873fc