In English "nervous" has a connotation of doubt along with fear. "He felt nervous he would not get the job," or "He was nervous about how he did on the English test." It can also have a connotation of fear along with excitement, such as "The child was nervous about riding the roller coaster for the first time," or "The man felt nervous as he got ready for his date."
The example you use of violently hitting the table seem more out of frustration or anger or exasperation. "The questions that the child asked exasperated his parent," or "The woman let out an exasperated sigh when she realized how much she had left to do before she could leave work."
The expression, "I have practiced just enough today" suggests that you did the very minimum amount of practice. Practice can be used as a verb: "I practiced this morning," or "I will practice this afternoon". So, you could say, "I practiced today," or "I practiced already" or "I finished my practice for today," or "I have finished practicing."
To say that you have finished something, say just "I finished" plus the thing. "I finished my work on the project" or "The project is done". "I finished my chores" or "My chores are done."
I hope these answers help.