I suspect that there are some people who do not become Christians because they (quite honestly) believe that they cannot stop sinning. (Most likely the sin they have in mind is sexual.)
They suppose that if they tried to become a Christian, but found that could not stop doing this particular sin, then they would be chucked-out of Christianity anyway, so why bother even trying...
In sum, they imagine that their inability to stop sinning prevents them becoming Christians - and that they must first stop sinning, then become a Christian: but they are as wrong about this is it is possible to be.
Christ came to save sinners, save people who are sinners, the Christian Church is for sinners.
You do not have to stop sinning before you become a Christian - the proper sequence is you become a Christian first, and then (try to) stop sinning.
But the fact is that nobody can stop sinning, they may defeat one sin (the one that most worries them) but always there will arise another or many more sins, and they will discover (after becoming a Christian) that they always have been sinning in ways they had not previously considered or noticed.
If people had to wait until after they were good before becoming a Christian: 1. There would be no Christians and 2. There would have been no need for Christ.
After becoming Christian, some have found the help to stop a particular type of sin which plagued them (for example alcoholism) - but many others have not been able to change.
But they are still Christians, indeed fully Christians, normal Christians; so long as they recognise the reality of their sin (that is, they do not pretend it is not a sin) and sincerely repent, and try again, and again.
So long, that is, as they recognize Christ as Lord. Everything else, the fruits of conversion, can follow afterwards, but even if they don't follow afterwards, you can still be Christian so long as that is your will.
(Anyone who imagines he is free of sin is not a Christian and is indeed in profound spiritual danger.)
All this is just a plain fact about Christianity, absolutely clear for 2000 years - and yet somehow modern people have been deceived into thinking that to be a Christians you must first be nice.
You may be a very bad sinner, you very probably are; and/but you can become a Christian now, at this very moment, without waiting, without preliminary preparations or purifications. Straight away.
There is nothing to stop you, and nothing in your past that would be able to prevent you.
Will to become a Christian because you believe it is true - be clear about that fact: and only then consider the difficult, indeed torturing matter, of 'joining a church', choosing a denomination, getting baptized or confirmed...
(All this can be a prolonged, difficult and dismaying business in a world where the Christian church, all denominations, have been so extensively corrupted and infiltrated by secular values, primarily Leftism. Still, we must will to become a Christian first, hold to that fact, and regard these institutional complications as necessary but secondary and subordinate challenges.)
You will not know, until you are a Christian, what the implications of Christanity may be, so you must become a Christian as a first step; just the first step - but it is the single most important step, a step into a new world which you can only begin to know only after you are in it.