One thing must be cleared that you arenot late at all. The minimum age to appear for SBI PO exam is 21 years old. And you are 21 now. So you stiil have time. And the most important thing is that you don't want to lose. Don't feel like that you are lost. Don't go for competition. There are students who qualify SBI PO in first time. But there are more students who can't qualify in the very first attempt. But they don't lose hope. They stuck to it until they reach their goal. So when you have time, you must prepare for the examination rather than thinking all these. If this is fear of failure, it can be cured only by not thinking about these. Just engage yourself in the preparation, you'll automatically forget this things.

First of all go through the entire syllabus of SBI PO. SBI PO prelims syllabus covers topics from Reasoning Ability, Quantitative aptitude and English language. So the main thing is that you have to concentrate on Aptitude more. Daily practice of aptitudes can help you a lot. Allot one day for one aptitude topic. After understanding and completing all the topics, you should solve practice sets available on various websites. There are many study materials available on internet. You can take help of video tutorials available free in YouTube. RS Aggarwal's Quantitative Aptitude for Competitive Examinations, A modern approach to Verbal and Non Verbal Reasoning - you can prepare from. If you find it difficult to study from different books, then make your own notes. This is a good habit, your memory retention will also improve.

Once done with syllabus you can move on to solving mock test, previous year exam papers. Then try to figure out your weak areas and work on them.

Hello Ayush,
This happens with everybody, once you were topper and then you might loose interest in studying or you looses consistency.
If you want success you have to feel motivated by yourself not from any other. You have to search for things which motivate you. I'm sure you'll able to crack any exam with motivation and dedication.
For clearing  SBI maximum one year is enough and minimum it will take 6 months.
So be sure what you want to do now and forget the past.
Thank you

Hlo aspirant,
Yes you can crack SBI. Any competitive exam require your dedication.If you have  faith in yourself and you really want to achieve your goal then focus on your target sharply.
Hope this answer is helpful for you.