Turning "CAN'T" into "I can't do it yet! " is an important step in developing mathematical confidence. 'Can't do it yet' give the option of returning and learning more. Learners can always learn more next time.
Too many young learners are hampered by their own expectations of inability. 'I can't ' needs to become 'I can't do it yet, implying that there might be a time in the future when the learner will say 'I can'.
Teachers should banish the phrase 'I can't' and encourage their learners to use 'I can't YET'.
This very small change has huge implications for the learner's own expectations; it sets them up to succeed eventually rather than to fail, and this expectation should be at the heart of all learning. The teacher can also praise learners for analysing their current situation as a part of their mathematical journey. It is also helpful to acknowledge the different times that different mathematicians take to solve their problems. Most of mathematics takes years to develop. It is more helpful to have problems that take different lengths of time to solve in the classroom. If learners understand problems take different lengths of time they are less likely to be upset if they are not able to solve something in two or three minutes.
In the mathematical arena things are perceived as easy if we can do them, and hard if we cannot YET do them. Making students aware of this distinction helps with the process of understanding. In the real mathematical arena, the journey of the struggle is more important that the solution. Again, teachers need to praise learners for being stuck - these learners are at the 'leading edge' of their learning. These learners are making genuine progress in their learning.
In the class if you are giving learners lengthier problems to solve it may also be useful to give them time to discuss their solutions and how they came to find the solution with each other.
[See Affective Obstacles to Mathematical Thinking]