Scruples can be dangerous things in the spiritual life. It causes a person to "see" sin where there is not and therefore, make bad decisions.
It is a kind of confirmation bias.
So with out ado ...
Occasions of sin are external circumstances--whether of things or persons--which either because of their special nature or because of the frailty common to humanity or peculiar to some individual, incite or entice one to sin.
It is important to remember that there is a wide difference between the cause and the occasion of sin. The cause of sin in the last analysis is the perverse human will and is intrinsic to the human composite. The occasion is something extrinsic and, given the freedom of the will, cannot, properly speaking, stand in causal relation to the act or vicious habit which we call sin. There can be no doubt that in general the same obligation which binds us to refrain from sin requires us to shun its occasion. Qui tenetur ad finem, tenetur ad media (he who is bound to reach a certain end is bound to employ the means to attain it).
Theologians distinguish between the proximate and the remote occasion. They are not altogether at one as to the precise value to be attributed to the terms. De Lugo defines proximate occasion (De poenit. disp. 14, n. 149) as one in which men of like calibre for the most part fall into mortal sin, or one in which experience points to the same result from the special weakness of a particular person. The remote occasion lacks these elements. All theologians are agreed that there is no obligation to avoid the remote occasions of sin both because this would, practically speaking, be impossible and because they do not involve serious danger of sin.
As to the proximate occasion, it may be of the sort that is described as necessary, that is, such as a person cannot abandon or get rid of. Whether this impossibility be physical or moral does not matter for the determination of the principles hereinafter to be laid down. Or it may be voluntary, that is within the competency of one to remove. Moralists distinguish between a proximate occasion which is continuous and one which, whilst it is unquestionably proximate, yet confronts a person only at intervals. It is certain that one who is in the presence of a proximate occasion at once voluntary and continuous is bound to remove it. A refusal on the part of a penitent to do so would make it imperative for the confessor to deny absolution. It is not always necessary for the confessor to await the actual performance of this duty before giving absolution; he may be content with a sincere promise, which is the minimum to be required. Theologians agree that one is not obliged to shun the proximate but necessary occasions. Nemo tenetur ad impossibile (no one is bound to do what is impossible). There is no question here of freely casting oneself into the danger of sin. The assumption is that stress of unavoidable circumstances has imposed this unhappy situation. All that can then be required is the employment of such means as will make the peril of sin remote. The difficulty is to determine when a proximate occasion is to be regarded as not physically (that is plain enough) but morally necessary. Much has been written by theologians in the attempt to find a rule for the measurement of this moral necessity and a formula for its expression, but not successfully. It seems to be quite clear that a proximate occasion may be deemed necessary when it cannot be given up without grave scandal or loss of good name or without notable temporal or spiritual damage.
Source: Catholic Encyclopedia