There is no such thing as being overly cautious when it comes to operating a tractor. Even though most of your work will probably be done in fields where the number of vehicles you encounter will be low, you still need to remain vigilant, as being alone in a field creates a different set of issues with which you may be faced. There are plenty of things that can go terribly wrong while working that can result in catastrophic consequences.
1. Just because you don't see it doesn't mean it isn't there, as is the case with underground hornet nests. Ever heard the expression, 'Mad as a hornet?' They say that for a reason, specifically because hornets can get pretty darn mad. Hornets also have no problem taking their anger out on you and they have the perfect weapon for the job-a non-barbed stinger that is not pulled from their bodies when they sting and can therefore be used time and time again to ruin your day. Hornets also come equipped with venom that contains a large amount of acetylcholine which is synonymous with pain. If you are allergic to this venom, a hornet sting can kill you. Watch the ground carefully for signs of a hornet's nest (such as holes or a hive that is grayish in color and looks similar to paper mache) and avoid any areas you feel are suspect. If you have an allergy to acetylcholine, be sure to have an Epipen handy at all times.
2. Be clear in your intent at all times. Directional changes are something that should be warned of, be it on the road or working in an area with other tractors or even people on foot. Don't ever assume someone knows what your next move is and will get out of the way on their own accord. If you signal clearly, it will better enable others to steer clear of your intended path, making a collision less likely. Even in a large work area, accidents happen, even accidents that seem obviously avoidable. If your tractor is not outfitted with turn signals, use your arm. Standard road-use signals are universal and work just fine for use amongst tractor operators, plus they are necessary for your safety when out on the road. There are also several other universal hand signals that are useful for tractor work. Acquainting yourself with them is vital to your safety and well-being.
3. Check your equipment before and after each use. Just because your tractor sat unused in the barn all week does not mean something could not have gone wrong with it. Rodents love to chew wires and could have severed something of the utmost importance, possibly even leading to a fire. Perhaps your hydraulics connector started to leak and has continued to leak unchecked for several days; now your hydraulics are out of commission. The only way you will know these things is if you carefully monitor your equipment on a regular basis. An occasional once-over is not enough; you must know what is normal for your tractor and check before and after each use to ensure that 'normal' is still the case.
Tractor work can be enjoyable but it needs to be safe, for both the operator and those nearby, up to and including livestock that may be grazing the very fields in which you are working. To stay safe, dedicate yourself to being vigilant at all times so everyone will get to go home after making hay.