Quite a lot of times I have to abandon a mission. Sometimes it is because my opponents are a tad to strong for me, sometimes because there is what I assume to be a bug.
Most often however it is because I cannot find objectives. Like a Trade vessel that moved away, an enemy vessel that after my respawn is nowhere to be found. Alien artifacts that are invissible, that single last trader in the huge asteroid cloud amidst all those other tradevessels. And while we are at it, finding npc's can be a big challenge as well.
Is there any way to find these? I know they glow, I know that sometimes the area is greyed out, I know that if I am lucky scan will help, I know that sometimes there is an I. But in the other cases?
For interactive objects and anomaly nodes hitting 'V' will do a sensor scan and point towards the nearest object. For the various NPC trader vessiel you need to find it depends on the mission. for "War is Good for Business" just keep scanning traders. There are more then 3 which will qualify. Just keep scanning until you get your 3. For singular trader in the mission in Romulan space, it's always the light trader. It won't move totally out of the area. You just need to keep scanning the vessels in that final area.
The freights in the asteroid clouds in the Exploration missions, I will totally agree they are hard to find at a times. But Cryptic is consistent when it comes to placing things on the Exploration maps. The disabled freighters are always in the middle. Take it slow and look for the odds shaped asteroid. For other type of space missions, there will be a visbly larger and different asteroid (or other things) that the mission objective will be near. And on ground missions, there are 5-6 "clearings" on the map which mission objectives will be placed. And there will always be a "path" which will connect the "clearings" on the maps. Sometimes it's extremely hard to see the "paths". but with practice you'll be begin to see the patterns on the maps.