On a more general note and in addition to all the sound advice above, things that can help one stop falling back into sin and maintaining one's repentance include (but are not limited to) the following:
1. Avoiding the places or situations where the issue arose in the first place.
2. Trying not to rationalise one's wrongs (ie keep thinking why did I do that? why was I so silly? etc etc).
Part of repentance is to stop the bad action and move on but if one keeps thinking about it and trying to rationalize it, a person may end up falling back into it because he has not managed to let it go of it fully.
What was done was done and one has no control over the past but only of the future.
3. The third one, in my opinion, is probably the most important and involves an individual having a real aversion and disgust for the sin he committed
As long as one looks back upon a sin and feels some sort of happiness in the indulgement thereof (eg a drunkard having a lingering fondness for the taste of wine even though he has stopped drinking), there will always be a part of him which may long to return to it.
If person can convince himself of the vile nature of the thing he did and the consequences it ended up having, the chances of him returning to it are materially reduced.
In effect, learn to belittle the wrong action and look upon it as something low and unworthy.
As ever, all the above is much easier said than done but, inshaAllah, we pray sister that Allah makes you firm in your repentance and raises your status because of it.