on what the Buddha taught
A popular translation for nīvaraṇā is hindrances.
Language is a bit ambiguous so understand that they don't feel as a hindrance to you, quite the contrary, but they are showstoppers to wisdom.
There are these five obstructions:
Kāmacchanda is a compound of kāma (lust) and chanda (desire) and stands for desire-with-lust or lustful desire. Desire with lust is what normally drives one to find happiness when engaged with the world, not when drawn back from it. It depends on improper attention to a sign of attractiveness (SN46.2). The more that keeps being fed, the more it grows. The analogy given in SN46.55 is about a bowl of water mixed with various dyes which when used as a mirror gives a distorted view. Thus when fed it consumes, obsesses, giving less room for more beneficial things. Under its influence we turn away from doing what is wise to do.
Byāpāda is an obstruction which depends on a sign of resistance (paṭigha) or friction if you will. With improper attention to this it appears and develops. The analogy given is about a bowl of water heated up which when used as a mirror gives a distorted view. The more heated up we are the less room we give for wise things. Heated up, out of friction, is generally an image for the display of anger. So lets call it just that.
Thinamiddha is a compound of thīna + middha. Thīna is to congeal, and middha is 'to be fat', torpor. They describe this one obstruction (not a conjunction; AN1.13). As obstruction it gets fed by the improper attention to things such as dislike or discontentment, weariness, yawning, drowsiness after a meal, mental sluggishness. The analogy given is a bowl of water covered up with weeds which couldn't be used as a mirror. Weed takes time to grow so one had no interest in keeping it tidy. Thus being bored or lazy; which makes you dull. Taken all together this obstruction seems to stand for that dullness. It wouldn't be to difficult to see dullness being a showstopper for wisdom.
Uddhaccakukkucca is a compound of uddhacca and kukkucca, describing this one obstruction. Uddhacca means something like agitation, excitement, and kukkucca bad doing, misconduct, bad character. Further is this obstruction fed by improper attention to mental unrest. Agitation over bad doings, fed by mental unrest, describes what we could call remorse. The analogy is a bowl of water being stirred (agitated) which when used as a mirror would give a distorted view. Being stirred with to much unrest to leave it alone. To busy crying over spilled milk which is already generally understood as not being helpful for anything, let alone wisdom.
Vicikicchā comes from vi+cikicchati, dis-reflect. The analogy says one can't use a bowl with muddy water in the dark as mirror. Thus a visual distinction can't be made. All look the same; without clarity, obscure, vague. When this as yoke is dealt with then there is that clarity and then there is no doubt. With doubt things might not be so clear, but at least they are clear enough to have doubt about them; they can be seen or considered (there is just no certainty about it) but when vague, lacking distinction, then as such it isn't even considered thus then there is not even that doubt. Unseen it will not be reflected on. This obstruction is fed by the improper attention to clarity lacking principles.
These five obstructions are all fed (either to appear or grow) by improper attention:
Nīvaraṇā obstructions.
Kāmacchanda lustful desire.
Byāpāda anger.
Thinamiddha dullness.
Uddhaccakukkucca remorse.
Vicikicchā unclarity.