Most pro se litigants fail in the court procedure area. There are many intricacies about what must be completed by when.
Determining jurisdiction can take a very long time, especially personal jurisdiction. These things set back cases repeatedly.
Additionally, many pro se litigants fail a 12(b)(6) motion. This means the other side files a motion saying that the opposing party failed to state a claim upon which relief can be granted. Typically, a pro se litigant fails to state with specificity each element of a claim and how the parties met each element.
If the litigant does not know how to remedy the situation, it will not succeed. Most judges in small claims overlook procedural deficiencies so long as they are not too burdensome on the opposing party.
If one is unsure how to proceed, contact an attorney.