I used to main soldier when I started playing TF2 (now I go back and forth between Spy and Medic). Something to always keep in mind is your health when you're rocket jumping. Rockets do a significant amount of self damage and even if you're using the rocket jumper, even fall damage will add up and every time you encounter an enemy after a rocket jump, you will most likely be at a lower than ideal health. Playing soldier is a balancing act between using rockets to move around while also using them in battle (usually), so you also need to pay attention to how many rockets you are using so you are never caught in an awkward situation where you really need it.