Personal development requires a huge amount of effort, discipline and vigour to break through the barriers of habit and reap the limitless rewards. But whilst it is important to be strict with ourselves, it must be done in a loving context. That means recognising that mistakes are an essential part of life; they are unavoidable opportunities that help form strong, happy personalities. The question is whether we learn from them or not. How much do we allow ourselves to repeat them? That will vary from situation to situation, and person to person, and in any case we must bear in mind that we are only human. Some things we won't change overnight, or even in the next 2 years.
I believe it is possible to strike a balance of sincere commitment to change, and acceptance of how we are in the present moment. Giving ourselves a pat on the back for our successes, no matter how small, and using humour to view our follies in the sometimes absurd, theatrical way events can happen, can really help us to relax and accept ourselves. Trying to put things into the bigger perspective of eternity may also get us back into that peaceful frame of mind after not achieving what we set out to do within a given time.
Try to embrace all weaknesses like a learning child might be embraced by its understanding parents. Sometimes it will fall over or make a mess through simple trial and error. The more you can accept yourself, the more you will be able to accept others. That makes for a much more peaceful environment and more harmonious relationships.