It is important that Christians understand how to interpret their failures in life - or else the response to failing can wreck the purpose of life.
One way failure wrecks a life is when - instead of acknowledging the failure, and repenting it - the person tells himself that it was Not a failure; and ends-up arguing and propagandising that it is not a failure - hence, the failure is asserted to be a virtue, instead of a sin.
This is moral inversion - the reversal of Good and evil, and probably the worst of all forms of evil; and it probably afflicts more people here and now (in numbers and as a proportion) than ever before in human history.
Another way that failure wrecks a life is when it is assumed that each failure to live by the ideal standards (e.g. never to sin) or to live in the ideal way (e.g. always to be at the highest level of consciousness) invalidates the ideal.
The way it goes is that: "Since I am incapable of perfection, I am a fraud; since my life is not wholly transformed by my faith - my faith is a sham. Because Christianity cannot abolish sin in me (or him, or her) it is useless. No matter how hard I try, I always keep failing; therefore it is futile to try."
These problems arise from a wrong understanding of the nature and function of this mortal life. What has been very helpful for me to recognise is that this mortal life comes between a pre-mortal eternity in which we were spirits (without bodies) and a post-mortal eternity in which we will be (those of us to choose it) resurrected immortal incarnates (with bodies).
This life is a finite period sandwiched between two 'infinities' - it is therefore not intended to be a permanent, fixed, or perfect mode.
If that is the structure of our life - past, present and future - what then is the function of this finite mortal segment that we are living now?
It is a time of experiencing and learning. And in order to experience, we will need a range of experiences - depending on our individual needs. In order to learn we will need some repeated experiences, we will also need new experiences.
Since learning is primarily directed at the eternity of post-mortal life; the outcomes in this finite mortal life are not, therefore, of a permanent, steady kind during this life. Therefore, current mortal life is not supposed to be an ideal state - or rather, the ideal mortal life is one that offers us the experiences we most need to learn-from. And these will seldom be unvarying ideality...
Indeed, mortal life has impermanence built-into it - there are many kinds of change; there is development, degeneration, disease, and death. For each person, his own 'baseline' is constantly changing - due to such processes.
The situation of mortal life is set-up to provide learning experiences; therefore it is Not set-up to provide the possibility of a life without failure.
Indeed, a mortal life without failure would (nearly always) be a failure as a mortal life!
Therefore Christians really should not be cast-down by failures as such; by imperfection as such; by the inevitability of sin, of change (including decline), of our absolute incapacity to live life to the fullest and at the highest level...
When we understand the nature and function of this, our mortal life; these become features, not bugs.
Note added from the comments: It is because we need to learn from failing that we are alive. If we
could live without failing - there would be no need to live.