There are many potential character qualities that are difficult, if not impossible, to carry at the same time. It is difficult and may even be impossible to be both assertive and cautious, or just and merciful, or patient and productive.
Any strict mutual exclusivity between character traits can be resolved through extreme specificity in how opposing character traits should interact. For example, you could be assertive when you have sufficiently strong reasons and cautious whenever you don’t.
These specifications are often not just when two positive qualities compete with one another, but also when you have a single quality that would be good to have in some cases and bad in others. For example, empathy is regarded as a universally positive quality by many, but it can easily become a vice when it is used in situations where doing so leads to greater harm through triggering even worse second order consequences. Your rule could be, “I will help relieve present suffering except where doing so would increase future suffering.”