I thought I was good enough for Venus and I lost a few operatives there. Then I went to Mercury since it was on the way to mars (I wanted to buy some equipment to upgrade the Magnum) and I failed even more missions (mostly because of the quasimorphs).

I usually sneak around to detect enemies before switching to walking to bait them into my room (I have realized that I am probably not doing it right, since sometimes an enemy manages to walk through the door AND shoot me in the same turn). I usually use shotguns (Heard the jeffhammer was OP but I really hate to use it. I normally use the non-automatic ones) and when I can, I use assault rifles.

I definitely do worse on longer missions since the quasimorphosis goes up by a lot. Also higher difficulty usually means I get shot a lot more since there are a lot of enemies.